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Descriptive epidemiology of thyroid cancer in Los Angeles County, 1972-1995
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Descriptive epidemiology of thyroid cancer in Los Angeles County, 1972-1995
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INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type o f computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely afreet reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zeeb Road, Ann Arbor MI 48106-1346 USA 313/761-4700 800/521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS The original manuscript received by UMI contains pages with indistinct, light and/or slanted print. Pages were microfilmed as received. This reproduction is the best copy available UMI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DESCRIPTIVE EPIDEMIOLOGY OF THYROID CANCER IN LOS ANGELES COUNTY, 1972-1995 By Tmirah Haselkom A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE (Applied Biometry/Epidemiology) August 1998 © 1998 Tmirah Haselkom Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 1393171 UMI Microform 1393171 Copyright 1999, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. U NIV ERSITY O F S O U T H E R N C A U F O R N IA T H E G R A D U A T E S C H O O L U N IV E R S IT Y P A R K L O S A N G E L E S . C A L IF O R N IA B0007 This thesis, "written by under the direction of hex. Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillment of the requirements for the degree of Tmirah Haselkorn Master of Science in ABED Date August 7, 1998 Dass THESIS COMMITTEE U J & ' l d U A CksirM M * Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS I would like to express my sincere appreciation to my thesis committee: Dr. Wendy Mack, committee chair, Dr. Leslie Bernstein, Dr. Susan Preston-Martin and Dr. Wendy Cozen for their close supervision, guidance, and expert advice. I would also like to thank my family and friends for their support and encouragement. ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Acknowledgements......................................................................................................ii List of Tables................................................................................................................ iv Abstract......................................................................................................................... v Chapter I. INTRODUCTION................................................................................1 1.1 The Thyroid and Tumor Origins...............................................1 1.2 Epidemiology by Subtype........................................................ 2 1.3 The Classification System....................................................... 3 1.4 Risk Factors..............................................................................3 1.5 Ionizing Radiation 4 1.6 History of Nonmalignant Thyroid Diseases 5 1.7 Iodine and Endemic Goiter 6 1.8 Diet 8 1.9 Hormonal and Reproductive Factors 10 1.10 Body Size/Weight Gain 11 1.11 Occupational Exposures 11 1.12 Genetics 13 H. METHODS 14 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m . RESULTS............................................................................................ 17 3.1 Overall Incidence Rates........................................................... 17 3.2 Incidence Rates by Race and Ethnicity................................... 17 3.3 Secular Trends..........................................................................18 3.4 Age-Specific Incidence R ates................................................. 18 3.5 Socioeconomic Status (SES)................................................... 19 3.6 Occupation................................................................................ 19 3.7 Histological Trends..................................................................20 3.8 Papillary Carcinoma.................................................................20 3.8.1 Incidence Rates by Race and Ethnicity...................... 21 3.8.2 Age-Specific Incidence Rates..................................... 21 3.9 Follicular Carcinoma................................................................22 3.9.1 Incidence Rates by Race and Ethnicity...................... 22 3.9.2 Age-Specific Incidence Rates.....................................23 3.10 Secular Trends in Papillary and Follicular Carcinomas 23 3.11 Medullary and Anaplastic Carcinomas...................................24 IV. DISCUSSION...................................................................................... 26 4.1 Incidence in Filipinos...............................................................26 4.1.2 Migration 27 4.1.3 Dietary Factors - Iodine Intake 28 4.1.4 Dietary Factors - Goitrogenic Vegetables 29 4.1.5 Volcanoes 30 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4.1.6 Benign Thyroid Diseases............................................ 30 4.2 Reproductive Factors................................................................30 4.2.1 Parity............................................................................ 30 4.2.2 Menarche..................................................................... 31 4.2.3 Menopause................................................................... 31 4.2.4 Exogenous Hormones................................................. 32 4.3 Secular Trends...........................................................................33 4.4 Socioeconomic Status and Occupation 34 4.5 Conclusions 36 Reference List 38 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 Average Annual Age-Adjusted Incidence Rates, Median Age at Diagnosis, and 5-Year Relative Survival Rate of Thyroid Cancer, by Histologic Type, SEER, 1973-1987.............................................................................................. 44 2 Occupations Showing Elevated Proportional Incidence Ratios (PIR) for Thyroid Cancer in Non-Spanish Sumamed Whites, Los Angeles County, 1972-1995 45 3 Distribution of Thyroid Cancer Cases by Ethnic Group, Histologic Type, And Sex in Los Angeles County, 1972-1995 46 4 Average Annual Age-Adjusted Incidence Rates (per 100,000) by Race - Medullary and Anaplastic Carcinomas, Los Angeles County, 1972-1995 47 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES Figure 1 Average Annual Age-Adjusted Thyroid Cancer Incidence Rates by Sex And Ethnicity, Los Angeles County, 1972-1995............................................48 2 Secular Trend in Thyroid Cancer Incidence by Sex, with Regression, Los Angeles County, 1972-1995 ............................................................................ 49 3 Age-Specific Thyroid Cancer Incidence Rates by Sex, All Races Combined, Los Angeles County, 1972-1995 ......................................................................50 4 Average Annual Age-Adjusted Thyroid Cancer Incidence Rates by Socio- Economic Status in Non-Spanish Sumamed Whites, Los Angeles County, 1972-1995..........................................................................................................51 5 Distribution of Thyroid Cancer by Histologic Type, Los Angeles County, 1972-1995.......................................................................................................... 52 6 Average-Annual Age-Adjusted Incidence Rates for Papillary Carcinoma By Race, Los Angeles County, 1972-1995 53 7 Age-Specific Incidence Rates, Papillary Carcinoma, Los Angeles County, 1972-1995.......................................................................................................... 54 8 Average Annual Age-Adjusted Incidence Rates for Follicular Carcinoma By Race, Los Angeles County, 1972-1995 55 9 Age-Specific Incidence Rates, Follicular Carcinoma, Los Angeles County, 1972-1995.......................................................................................................... 56 10 Secular Trend in Papillary and Follicular Carcinoma, Los Angeles County, 1972-1995 57 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT The descriptive epidemiologic features o f thyroid cancer in Los Angeles County were studied for the period 1972-1995, using data from the University of Southern California Cancer Surveillance Program. For all races combined, the age-adjusted incidence rates were 2.5 per 100,000 in males and 6.0 per 100,000 in females. In each major ethnic group, the age-adjusted incidence rates among women were more than twice the rates for men. Blacks had the lowest rates of thyroid cancer while Filipinos demonstrated the highest incidence rates. During the 23-year period, there was an increase in papillary carcinoma and a decrease in follicular carcinoma. Risk factors such as benign thyroid nodules and goiter, hormonal and reproductive factors, occupational exposures, and diet are discussed in reference to the elevated incidence rates among Filipinos, as well as the clear preponderance o f thyroid cancer in females. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I INTRODUCTION Thyroid cancer, a relatively rare disease accounting for only 1.3% o f all cancers, represents the majority (92%) of the cancers of the endocrine glands (Correa and Chen, 1995). The U.S. Surveillance, Epidemiology, and End Results (SEER) cancer registries reported the 1987-1991 age-standardized incidence rates for thyroid cancer as 2.5 per 100,000 for males and 6.4 per 100,000 for females. Long-term survival for thyroid cancer is high, with a mere 0.14% of male and 0.25% of female cancer mortality attributed to thyroid cancer (Boring et al., 1994 cited in Ron, 1996). An estimated 17,000 new thyroid cancer cases will be diagnosed in the United States in 1998 and an estimated 1200 persons with thyroid cancer will die in the same year (ACS, 1998). This paper examines the descriptive epidemiology o f thyroid cancer in Los Angeles County between 1972-1995. Using epidemiologic measures, it examines patterns of incidence with respect to gender, age, ethnicity, histology, and secular trend and offers potential hypotheses to explain the trends found in Los Angeles County. This evaluation provides an update to the first descriptive epidemiologic study in Los Angeles County (Preston-Martin and Menck, 1979) which used incidence data from 1972-1976. 1.1 The Thyroid and Tumor Origins The thyroid gland is located in the neck just below the larynx and is composed of two lobes that lie on either side of the trachea united by a narrow band of tissue, the isthmus (McCance and Huether, 1990). The thyroid gland produces thyroxine and calcitonin, two hormones which control the rates of metabolic processes throughout the l Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. body (Purves et al., 1992). The majority of thyroid tumors originate in the follicular cells, which line the thyroid follicle, and synthesize thyroxine. Increased levels of thyroid hormones trigger a proliferation of the follicular epithelium, producing projections into the follicular lumen in the form of papillae, once the lining of the follicle is filled. After differentiation, either follicles or papillae are produced and are, consequently, classified as “follicular” or “papillary” carcinomas. Tumors that do not demonstrate recognizable thyroid origins are termed “anaplastic” or “undifferentiated.” Calcitonin is produced in the perifollicular C cell, which serves to regulate calcium metabolism. Tumors arising from these cells are classified as “medullary” carcinomas (Correa and Chen, 1995). L2_Epidemiology b .y Subtype The most common histologic type of thyroid cancer in the U.S. is papillary carcinoma which represents about 70% of total cases in both sexes and among whites, but is not as common among blacks (Correa and Chen, 1995). Follicular carcinoma represents about 20% of thyroid tumors (range, 10-40%), and occurs more frequently in blacks than in whites (31.0% vs. 16.7%) (Ron, 1996; Correa and Chen, 1995). Medullary carcinoma is relatively rare and a female preponderance has been observed in whites, but not in blacks (Correa and Chen, 1995). Medullary and anaplastic carcinoma are both relatively rare, and, together, account for between 5% and 15% of thyroid cancer incidence (Ron, 1996). Papillary carcinoma has the highest survival rate of the histologic types, with an overall 5-year survival rate o f 98.1%, followed by follicular carcinoma which is characterized by a 5-year survival rate of 92.0% (Correa and Chen, 1995). The overall 5- 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. year survival rate for medullary carcinoma is about 82%. Anaplastic carcinoma, however, is very aggressive and is nearly always fatal, resulting in an overall 5-year survival rate o f less than 10% (Correa and Chen, 1995). Females consistently show higher incidence rates for thyroid cancer than males. For papillary and follicular cell types, the female-to-male ratio is approximately 3:1. When evaluated over all ethnic groups, medullary and anaplastic carcinomas have no clear preponderance for either gender. Medullary carcinoma rates, however, are higher in white females than in white males. The mean age at diagnosis is 41 years for papillary carcinoma, about 50 years for follicular and medullary, and 71 years for anaplastic carcinoma (Correa and Chen, 1995). Table I summarizes the epidemiologic patterns of the individual histologic types. 1.3 The Classification System The classification system used for this paper applies the International Classification of Diseases for Oncology (ICD-O) morphologic coding system used by the Surveillance, Epidemiology, and End Results (SEER). This method characterizes papillary and follicular carcinoma by nuclear morphology and mode of progression, as opposed to the cellular architecture. This system has become the accepted criteria for classifying the different thyroid tumors (Correa and Chen, 1995). 1.4 Risk Factors Several possible risk factors for thyroid cancer have been evaluated, including ionizing radiation, a history of nonmalignant thyroid diseases, iodine (either deficiency or 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. excess), diet, hormonal and reproductive factors, body size and weight gain, occupational exposures, and genetics. 1.5 Ionizing Radiation Exposure to ionizing radiation as a prime risk factor for thyroid cancer was first recognized in 1950 (Duffy and Fitzgerald). Since then, many studies have confirmed this relationship (Conard, 1984; McTieman et al., 1984a; Shore et al., 1985; Thompson et al., 1994). Radiotherapy was widely used between 1920-1960 for the treatment of Hodgkin’s disease and benign head and neck conditions, such as tinea capitis, thymic enlargement, and enlarged tonsils, as well as for skin disorders such as cutaneous haemangioma and acne (Lundell et al., 1994; Langsteger et al., 1993). As a result, thyroid cancer has become one of the strongest indicators of therapeutic radiation exposure during childhood (Schneider et al., 1993). A case-control study in Connecticut females estimated that 9% of the incident thyroid cancer cases could be attributed to prior head and neck irradiation (Ron et al., 1987). In addition, dose-response and early age at exposure relationships between radiation and the development of thyroid carcinoma have been established (Schneider et al., 1993; Lundell et al., 1994; Thompson et al., 1994). A multitude o f studies from different countries have all confirmed significantly increased risks of thyroid carcinomas following therapeutic radiation exposure during childhood (Ron, 1996). The use of radiotherapy in medical practice has decreased. It is expected, therefore, that the attributable risk of radiation exposure in thyroid cancer will decrease as well. The increased risk of thyroid carcinoma due to radiation exposure has also been documented among atomic bomb survivors, particularly those who were children at the 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. time o f exposure. Increased rates of thyroid cancer have also been reported in the Bikini and M arshall islands (Conard, 1984), as well as around atomic bomb test sites in Utah and Nevada (Caldwell et al., 1983) following radioactive fallout due to nuclear bomb testing. These results are supported by studies conducted in Japan where researchers found a 15% increase in risk for thyroid cancer among those who were residents of Hiroshima and Nagasaki in October of 1950 (Thompson et al., 1994). In addition, an increased incidence of thyroid cancer in children was reported in the Ukraine and Belarus following the Chernobyl reactor accident in 1986 (Prisyazhiuk et al., 1991; Kazakov et al., 1992). A recent study that investigated the incidence of thyroid cancer within three districts close to Chernobyl showed that these areas had the highest incidence density of thyroid cancer for children younger than 15 years in 1986 (Bleuer et al., 1997). Furthermore, the geographical distributions of childhood incidence rates showed a striking similarity to the geographical patterns of radioactive iodine isotope (1 3 1 I) contamination. 1.6 History of Nonmalienant Thyroid Diseases Prior nonmalignant thyroid diseases in relation to thyroid cancer have also been examined. Thyroid cancer risk appears to be increased among those who have suffered from thyroid adenoma, simple or endemic goiter, multiple nodular goiter, thyrotoxicosis and Hashimoto’s thyroiditis (Ron, 1996). In one study, an almost eight-fold risk of thyroid cancer was found in those subjects diagnosed with any type of benign thyroid disease (D’Avanzo et al., 1995). Evidence of a link between benign thyroid nodules and an increased risk of thyroid cancer has been demonstrated in various studies (Preston- 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Martin et al., 1987; Preston-Martin et al., 1993; Ron et al., 1987). Preston-Martin et al. (1987) found an almost fifteen-fold greater risk for thyroid cancer among those women with a history o f benign hyperplastic thyroid disease (including thyroid enlargement, goiter, and nodules) than among those with no such disease history. In a population- based study in Connecticut, 4% of the incident thyroid cancers were attributed to goiter and 17% to thyroid nodular disease (Ron et al., 1987). It has been suggested that benign thyroid tumors may be actual precursor lesions for thyroid cancer. 1.7 Iodine and Endemic goiter Iodine deficiency has also been considered as a possible risk factor for thyroid cancer by potentially acting as both a carcinogen and as a tumor promotor by inhibiting the secretion of TSH (thyroid-stimulating hormone secreted from the pituitary gland) (Ron, 1996). The result of this deficiency in iodine can cause a malfunction of the thyroid gland called goiter, which is common in mountainous areas and regions far from the oceans where there is little iodide in the soil or water (Purves et al., 1992). In 1928, Wegelin found that the rate of thyroid cancer in Bern, where endem ic goiter due to iodine deficiency is common, was ten times higher than in goiter-free Berlin. A more recent study found that residence in an iodine-deficient environment for more than 20 years was associated with an increased risk of thyroid cancer (Galanti et al., 1995). Additional studies have also shown that in areas where endemic goiter is prevalent, a higher incidence of thyroid cancer has also been observed, in particular, for follicular and anaplastic carcinomas (Langsteger et al., 1993; Pettersson et al., 1996). Currently, the highest known incidence rates of follicular and anaplastic carcinomas are in regions of 6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. extreme endemic goiter in Columbia. Iceland which, overall, has the highest incidence rate of thyroid cancer in western countries, is not an area with iodine deficiency (Langsteger et al., 1993). In fact, areas characterized by high iodine intake, such as the island populations of the Pacific, have the highest thyroid cancer incidence rates in the world (Blot et al., 1997). The introduction of iodized salt to control goiter has shown mixed results. A decrease in thyroid cancer mortality was seen in Switzerland after iodine supplementation (Wynder, 1952). This intervention, however, led to an increase in incidence of papillary carcinoma, and ultimately, a shift in the ratio of papillary to follicular carcinomas. A similar trend was also seen in Austria following iodine supplementation (Langsteter et al., 1993). In the United States, however, the introduction of iodized salt between World War I and World War II did not decrease thyroid cancer incidence or mortality from 1939-1941 to 1949-1951 (Pendergrast et al., 1961). In addition, incidence rates of thyroid cancer were not correlated with incidence rates of endemic goiter in Nordic countries (Franssila et al., 1981). One possible explanation for these inconsistent results is the geographical variation in histology. Some studies have shown that endemic goiter areas appear to be associated with higher risks of follicular and, perhaps, anaplastic thyroid cancer, whereas iodine-rich areas have been associated with an elevated risk of papillary carcinoma (Doniach, 1971; Williams et al., 1977). In Japan, for example, iodine intake and, consequently, the incidence of papillary carcinoma are higher than in western countries and endemic goiter areas (Langsteger et al., 1993). 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.8 Diet Cruciferous vegetables (such as broccoli and cauliflower) have been shown fairly consistently to have a protective effect against thyroid cancer. It has been hypothesized that this protection may be due to an inhibitory effect of indole components, isothiocyanates, and phenols contained in these vegetables (National Academy of Sciences, 1983). In large quantities, goitrogens (contained in cabbage and brussel sprouts) have been shown to cause thyroid cancer in laboratory animals by blocking iodine uptake and the synthesis of thyroid hormones, ultimately causing the pituitary gland to increase TSH secretion. These effects, however, are unlikely to contribute to the direct development of thyroid cancer in most populations, since the amount of goitrogens consumed is too low. Studies have shown that populations that consume goitrogens as a major part of the diet and reside in areas of endemic goiter also have elevated levels of TSH and abnormal thyroid states (Franceschi et al., 1990; McLaren and Alexander, 1979). Contrary to expectation, case-control studies from Hawaii and Connecticut found protective effects of some goitrogenic vegetables (Kolonel et al., 1990; Ron et al., 1987). Numerous other studies have found reduced risks for thyroid cancer associated with cruciferous vegetables. A pooled analysis of four case-control studies conducted in Europe found protective effects for most types of vegetables and all fruit, with significant inverse trends for carrots, green salad and citrus fruits (Franchesi et al., 1991). A case- control study in Italy found a significant trend of increasing protection against thyroid cancer with increasing vegetable consumption, however, no association with fruit was detected (Negri et al., 1991). In the Connecticut study, all vegetables were found to 8 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. decrease the risk of thyroid cancer, however, the results were not statistically significant (Ronetal., 1987). Results of studies of the effects o f starchy foods and meats on thyroid cancer risk have shown mixed results. In European studies, cases tended to eat more starchy foods such as pasta or rice, bread, pastry, and potatoes than controls. In addition, consumption of some meats such as chicken and poultry, cooked ham, salami and sausages increased risk for thyroid cancer (Franceschi et al., 1991). In contrast to these observations, thyroid cancer risk decreased with increased consumption of chicken, beef, and bread in the Connecticut study (Ron et al., 1987). In the European pooled analysis, consumption of raw ham and fish reduced the risk of thyroid cancer (Franchesi et al., 1991). Shellfish contains large amounts of iodine. The Connecticut study showed an increased risk of follicular, but not papillary, carcinoma among those with a frequent diet of shellfish relative to those who were infrequent consumers o f shellfish (Ron et al., 1987). This result was confirmed in the Hawaii study (Kolonel et al., 1990) which found that among women, shellfish consumption was associated with an increased risk of thyroid cancer over all histologic types. In addition, cases in this study consumed more harm ha, a fermented fish sauce, than controls. Finally, a case-control study of thyroid cancer in Shanghai found that, overall, cases consumed more fish and shellfish than controls, however, there was no significant trend in risk with increasing frequency of consumption (Preston-Martin et al., 1993). 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Some have suggested that alcohol consumption promotes thyroid cancer by inducing TSH secretion (Breslow et al., 1974 and Williams, 1976). This association, however, was not confirmed either in the Connecticut study (Ron et al., 1987) or in the European pooled analysis (Franchesi et al., 1991). Vitamin D intake is another risk factor for thyroid cancer. It is believed that v itam in D increases the risk for medullary carcinoma by increasing calcitonin production and a precursor lesion called C-cell hyperplasia (Williams, 1979). Ron et al. (1987) found an increased risk in those who took vitamin D supplements regularly compared to individuals who never took any specific vitamin regularly. The positive association between vitamin D and thyroid cancer was primarily a result of a fourfold risk of medullary carcinoma. 1.9 Hormonal and Reproductive factors The fact that women have greater risk of thyroid cancer than men may be due to their higher levels of TSH during puberty, pregnancy, and menstrual cycles, which ultimately increase thyroid cell proliferation and the risk of thyroid cancer (Correa and Chen, 1995; Preston-Martin et al., 1987). Several case-control studies have shown that parity increases thyroid cancer risk (Preston-Martin et al., 1987; Preston-Martin et al., 1993; Ron et al., 1987; McTieman et al., 1987b). In addition, some studies (Preston- Martin et al., 1987; Preston-Martin et al., 1993; Ron et al., 1987; Kolonel et al., 1990) found an increased risk associated with miscarriage. Galanti et al. (1996), however, did not find any clear association with miscarriage or with parity. 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Some studies have shown an elevated risk for thyroid cancer with the use of oral contraceptives (Preston-Martin et al., 1987; Preston-Martin et al., 1993; Ron et al., 1987; McTieman et al., 1984b). Galanti et al. (1996) and other studies, however, did not find an increased risk for thyroid cancer with oral contraceptive use. Finally, McTieman et al. (1984b) found a slight increase in risk for those women who had used postmenopausal estrogens, however, the results were not statistically significant. 1.10 Body Size/Weieht gain The role of weight gain in the development of thyroid cancer has been investigated. The case-control study of thyroid cancer in Connecticut found that among women, those who were obese during adolescence and adulthood had a statistically significant increased risk of thyroid cancer (Ron et al., 1987). In addition, the study conducted in Shanghai (Preston-Martin et al., 1993) found that cases had gained more weight than controls from menarche to highest non-pregnant weight. Kolonel et al. (1990) also found an increased risk associated with greater weight and obesity for both men and women, with the results for men showing statistical significance. 1.11 Occupational Exposures Persons with occupations involving radiation exposure have consistently been shown to have increased thyroid cancer risk. Two case-control studies that were conducted in different regions of Sweden found similar results. The first study evaluated risk for papillary carcinoma only and showed that those who performed work with diagnostic x-ray investigations had a nearly three-fold elevated risk for papillary carcinoma (Hallquist et al., 1993). The second study was restricted to female papillary 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. cancer of the thyroid; it showed that women who were occupationally exposed to x-rays were twice as likely to develop papillary carcinoma as women who were not exposed (Wingren et al., 1995). In addition, dentists and dental assistants were found be at increased risks for papillary carcinoma. Both of these studies also found that occupations such as teachers and shoemakers were associated with increased risks for papillary carcinoma. Another study found elevated risks in textile workers, petroleum industry workers, pharmacists, drivers, and workers in the canning and preserving industry (Carstensen et al., 1990). The association between chemical exposures and thyroid cancer has been investigated as well. Hexacholorobenzene, which is a chlorinated hydrocarbon that was formerly used as a fungicide, but is now produced by industrial emissions as a secondary outcome of the production of organochoiorides, has been shown to increase thyroid cancer risk among males, but not in females (Grimalt et al., 1994). 2,3,7,8- tetrachlorodibenzo-p-dioxin, or TCDD, a type of chlorophenoxy herbicide, has been shown in two separate studies to be associated with increased thyroid cancer risk. The first study, which evaluated mortality in production workers and sprayers from ten different countries using a historical cohort, found excess thyroid cancer mortality among exposed workers (Saracci et al., 1991). The second study, conducted in a specific region in Italy after an accidental explosion in a chemical plant, found a nearly five-fold increase in incidence relative to the surrounding non-contaminated area; however, this result was not statistically significant (Pesatori et al., 1993). Finally, a nonsignificant excess in thyroid cancer mortality has been shown among a cohort of dry cleaners (Blair et al., 12 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1990). Exposures in the dry cleaning industry include many organic solvents, such as carbon tetrachloride, Stoddard solvent, tetrachloroethylene, trichloroethylene, and fluorocarbons. 1.12 Genetics The role of genetics in the development of thyroid cancer has been evaluated, particularly for medullary carcinoma. There are two types of medullary thyroid carcinoma (MTC). The first is sporadic and typically occurs in 7 5 - 8 0 % of the medullary cancer cases (ACS, 1 9 9 8 ). Familial medullary thyroid carcinoma (FMTC) is the second type and has been shown to be inherited in an autosomal dominant pattern with penetrance of nearly 1 0 0 % . About 2 0 -2 5 % of medullary carcinoma is considered familial with a major portion associated with multiple endocrine neoplasia (MEN) syndrome (Schimke et al., 1 9 6 8 ). Studies have also isolated DNA mutations that cause some fo rm s of papillary carcinoma. Most involve mutations in the ret oncogene which are acquired (somatic mutations) rather than inherited (ACS, 1 9 9 8 ). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER n METHODS The Los Angeles County/University of Southern California Cancer Surveillance Program (CSP) was established in 1970 to collect information on all newly diagnosed cancer cases am ong the residents of Los Angeles County. The CSP has provided complete ascertainment of cancer in Los Angeles County since 1972 and currently m aintains over 1,000,000 records, adding more than 37,000 incident cancer cases per year. Since 1987, the CSP has employed elements of an active and a passive reporting system: each hospital or other medical institution submits information to the CSP for cancer cases seen at that facility. Each entry in the registry is later matched by the CSP to a pathology report obtained under active surveillance to ensure completeness of reporting. Also, previous cancer diagnoses that are unrecognized in Los Angeles County residents and identified as a result of searching computerized death records are traced back to patient records in hospitals or other facilities so that data can be collected. Prior to 1987, all data collection was done by CSP staff (active surveillance). For each patient, the CSP identifies demographic descriptors such as race- ethnicity, age, and gender. Racial group is identified primarily from the medical admission record or medical chart. The CSP divides whites into “Spanish sumamed” and “non-Spanish sumamed” using Spanish surname lists prepared by the Bureau of the Census for 1970 and 1980. Other ethnic groups identified include Black, Chinese, Japanese, Filipino, and Korean. All remaining ethnic groups are classified as “Other.” 14 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Each case is also identified by subsite, histology, year of diagnosis, place of residence (at diagnosis), birthplace, marital status, religion, occupation and industry (at diagnosis) and extent of disease (stage) at diagnosis. Socio-economic status (SES) is defined by the SES classification assigned to each case’s census tract of residence when diagnosed with cancer. The SES classification is based on the U.S. Census data on household income and education of the residents of that census tract. Status is then assigned using a ranking system between 1 and 5, with a low SES marked by 5 and a high SES indicated by 1 (Liu et al., 1998). To calculate incidence rates, (age, gender, and race-specific) populations at risk for the county and for SES groups within census tracts from 1972 through 1995 have been estimated using U.S. Census data for the years 1970, 1980, and 1990, with linear interpolation and extrapolation for the non-census years. Age-adjusted incidence rates per 100,000 were calculated by direct standardization using five-year age groupings and the 1970 U.S. population as the standard. Ninety-five percent confidence intervals for age-adjusted rates were based on the binomial estimate of the variance of the rate. Finally, since population denominators are not available by occupation or industry, the proportional incidence ratios (PIRs) were calculated for occupational categories. The PIR is the ratio o f the observed number of cancer cases in a given occupation to that expected based on the age-specific distribution of occupations across all cancer sites. PIRs are calculated by dividing the total number of observed cancers in each particular occupation for all ages within each of the race- ethmcity groups, by the total number of expected cases (with the same parameters) and 15 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. multiplying by 100 (Ross et al., 1991). The following report utilizes the CSP data for cases diagnosed between 1972-1995. 1 6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER ID RESULTS 3.1 Overall Incidence Rates There were 8,820 new cases of thyroid cancer reported in Los Angeles County between the years 1972-1995. Of these cases, 2,311 (26.2%) were in males and 6,509 (73.8%) were in females. The average annual age-adjusted incidence rate (AAIR) for males was 2.48 per 100,000 males (95% C.1.2.37-2.58) and for females was 5.99 per 100,000 females (95% C.I. 5.85-6.14). 3.2 Incidence Rates bv Race and F.thnicitv In each major ethnic group, the age-adjusted rates for thyroid cancer among women were more than twice the rates for men (Figure I). The black population in Los Angeles County demonstrated the lowest rate for females at 3.38 per 100,000 (95% C.I. 3.04-3.71). Among males, Koreans had the lowest rate at 1.28 per 100,000 (95% C.I. 0.51-2.05). The Filipino population displayed the highest rates of thyroid cancer for both sexes (4.44 per 100,000 for males, 95% C.I. 3.34-5.55); (11.33 for females, 95% C.I. 9.81-12.85). Chinese and Japanese males and females also had relatively low incidence rates. Rates in Spanish sumamed whites (2.19 per 100,000 for males, 95% C.I. 1.92- 2.47; 6.59 per 100,000 for females, 95% C.I. 6.20-6.98) were comparable to the rates among the non-Spanish sumamed whites (2.87 per 100,000 in males, 95% C.I. 2.73-3.01; and 6.55 per 100,000 in females, 95% C.I. 6.34-6.76). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.3 Secular Trends Thyroid cancer rates among among males living in Los Angeles County were fairly stable from 1972-1995 (Figure 2). In general, incidence rates throughout the study period were characterized by minor fluctuations in incidence rates. The highest rate for thyroid cancer for males is seen in 1992, where the incidence rate sharply increased to 3.11 per 100,000. The AAIR’s increased approximately 1.5% per year (absolute change 0.007 per 100,000 per year) over the 23-year period. The 2-3 fold female preponderance in AAIR’s relative to males was evident throughout the study period (Figure 2). Sharp increases in incidence were seen in 1984 and in 1993. Females also exhibited an overall increasing trend in incidence during the late 1980’s and demonstrated the highest incidence rate in 1993 (AAIR=7.55,95% C.I. 6.76-8.34). The incidence rates increase about 1% per year (absolute change 0.04 per 100,000 per year) over the study period. 1.4, Aee-Specific Incidence Rates For both genders, the incidence rate of thyroid cancer increases progressively with age for all races combined (Figure 3). Rates are similarly low among young children of both genders. Females, however, exhibit a remarkably rapid increase in incidence during reproductive years and then a decline around the menopausal period. Until age 29, the incidence rates for women are about five times the rate for males. The highest incidence rate occurs during the ages o f 50-54 at 11.45 per 100,000. The increase in thyroid cancer rates by age among males shows a more gradual progression, with peak incidence occurring between ages 75-79 (8.26 per 100,000), and rates decreasing thereafter. 18 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.5 Socioeconomic Status (SES) Figure 4 shows thyroid cancer incidence rates by social class for both genders for non-Spanish sumamed whites. Both males and females show a distinct linear trend in incidence with the highest thyroid cancer rates occurring among the highest socioeconomic group. The AAIR for the highest SES group among males was 3.70 per 100,000 (95% C.I. 3.40-4.00) and for females was 7.18 per 100,000 (95% C.I. 6.77-7.58). The AAIR in the lowest SES group was 1.82 per 100,000 (95% C.I. 1.41-2.23) for males and 4.09 per 100,000 (95% C.I. 3.46-4.72) for females. The pattern observed for non- Spanish sumamed whites was not seen for the other racial/ethnic groups. 3.6 Occupation The occupational data presented are limited to non-Spanish sumamed whites due to the small number of thyroid cancer cases among the other ethnicities. Among non- Spanish sumamed white males, a greater than expected number of thyroid cancer cases occurred among lawyers (PIR= 156.2, 95% C.I. 104.6-224.4; n=29 cases), dentists (PIR=388.4, 95% C.I. 200.5-678.5; n=12 cases), pharmacists (PIR=294.4, 95% C.I. 107.5-640.9; n=6 cases), physicians, (PIR=240.6,95% C.I. 166.6-336.2; n=34 cases), radiologic technicians (PIR=425.8,95% C.I. 137.2-993.6; n=5 cases), economists (PIR=239.8, 95% C.I. 103.2-472.5; n=8 cases), psychologists (PIR=349.7, 95% C.I. 150.6-689.0; n=8 cases), teachers at the college and university level (PIR=250.4, 95% C.I. 129.2-437.4; n=12 cases), musicians and composers (PIR=200.2, 95% C.I. 103.3- 349.8; n=12 cases), and managers and administrators (PIR=116.9,95% C.I. 100.8-134.9; n=187 cases) (Table 2). 19 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Among non-Spanish sumamed white females, a significantly higher number of observed than expected thyroid cancer cases occurred among psychologists (PIR=220.1, 95% C.I. 117.1-376.3; n=13 cases), saleswomen (PIR=240.3,95% C.1.109.7-456.3; n=9 cases), bookkeepers (PIR=331.2, 95% C.1.120.9- 720.9; n=6 cases), stenographers (PIR=232.6,95% C.I. 106.1-441.6; n=9 cases), and homemakers (PIR=110.2, 95% C.I. 102.7-118.0; n=813 cases) (Table 2). The increased number of thyroid cancer cases found in the above occupations were consistent with those found when the data were analyzed by industry. 3.7 Histological Trends Figure 5 displays the distribution of thyroid cancer cases in Los Angeles County by histologic type for each sex. The distribution of histologies for both genders was similar. Papillary carcinoma was most common in males and females, representing 72% and 77% o f the total thyroid cancer cases, respectively. Follicular carcinoma was the next most common type of thyroid cancer, occurring in 16% o f the cases in males and 14% of the cases in women, followed by medullary, anaplac and the other less frequent histologies. Table 3 shows the distribution of thyroid cancer cases by ethnic group and histologic type. Blacks had the highest proportion of follicular carcinomas, while the Asian groups had the highest proportion of papillary carcinomas. 1JL Papillary Carcinoma During the period 1972-1995, papillary carcinoma accounted for 76% (6684 cases) of the total invasive thyroid cancer cases in Los Angeles County. The overall age 20 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. adjusted incidence rate for males and females during this time period was 1.74 per 100.000 (95% C.1.1.66-1.83) and 4.63 per 100,000 (95% C.1.4.50-4.76), respectively. 3.8.1 Incidence Rates bv Race and Ethnicity The black population had the lowest age-adjusted incidence rate o f papillary carcinoma for both males and females at 0.76 per 100,000 in males (95% C.I. 0.58-0.95) and 2.22 per 100,000 (95% C.I. 1.94-2.49) in females (Figure 6). Japanese and Chinese populations showed low incidence rates in comparison to the other ethnicities. Filipinos had the highest age-adjusted incidence rate for this histologic type for both men and women at 3.87 per 100,000 (95% C.I. 2.84-4.91) and 9.61 per 100,000 (95% C.I. 8.21- 11.02), respectively. Korean females demonstrated the second highest incidence rate at 6.04 per 100,000 (95% C.I. 4.60-7.47). Rates for Spanish sumamed whites and non- Spanish sumamed whites were similar. 3.8.2 Age-Specific Incidence Rates Age-specific incidence curves for papillary carcinoma showed major differences by sex (Figure 7). Generally, females had higher incidence rates than did males at all ages. The rate of increase for females before age 35 was much higher than that for males. In females, rates rise sharply after puberty and begin to plateau between 35-39. The peak incidence at 8.91 per 100,000 occurred between ages 50-54. Incidence rates for females drop rapidly after age 54. The incidence curve for males increased with age at a more gradual rate than females, plateaued between ages 55-74, and reached the peak at ages 75- 79. 21 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.9 Follicular Carcinoma Follicular carcinoma is the second most common type of invasive thyroid cancer, accounting for 15% (1287 cases) of all thyroid cancer cases diagnosed in Los Angeles County between 1972-1995. During this period, follicular carcinoma represented 23.2% of the total thyroid cancer cases in blacks, but only 14.6% of the total cases in non- Spanish sumamed whites. The follicular carcinoma cases among Filipinos represented 11% of the total thyroid cancer cases in this ethnic group. The overall age-adjusted incidence rate for follicular carcinoma in men was 0.40 per 100,000, whereas the rate for women was approximately twice that o f males at 0.86 per 100,000. 3.9.1 Incidence Rates bv Race and Ethnicity The male population in Los Angeles County did not show major disparity between the ethnic groups in incidence rates for follicular carcinoma. Blacks, Filipinos and Spanish sumamed whites displayed approximately identical rates (Figure 8). The Asian male populations showed the lowest age-adjusted incidence rates for follicular carcinoma, while non-Spanish sumamed white males demonstrated the highest age- adjusted incidence rate at 0.46 per 100,000 (95% C.I. 0.41-0.52). Among women, Filipinas maintained the highest age-adjusted incidence rate of all the ethnicities at 1.27 per 100,000 (95% C.I. 0.78-1.76). Spanish sumamed females achieved higher rates for follicular carcinoma than non-Spanish sumamed white females, in contrast to the comparable rates seen previously between the two groups in all thyroid carcinoma cases combined and papillary carcinoma. While black females showed the lowest incidence 22 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. rate for papillary carcinoma compared to the other ethnicities, their rates for follicular carcinoma surpassed the rates for Korean, Japanese, and Chinese females. 3.9.2 Age-Specific Incidence Rates In contrast to the strikingly different age-specific curves for males and females that characterize papillary carcinoma, the general pattern o f age-specific incidence rates for follicular carcinoma for both genders are quite similar (Figure 9). Although rates for females are still higher than those for males, the difference between them is not as great as that seen between the genders for papillary carcinoma. In addition, the incidence rates for follicular carcinoma for both men and women show comparable curves. The incidence rates rise gradually with increasing age, and show women reaching the peak age at diagnosis between the ages of 70-74 (2.30 per 100,000) and men between the ages of 75-79 (1.97 per 100,000). Like papillary carcinoma, rates in females rise sharply at the beginning of the reproductive period. 3.10 Secular Trends in Papillary and Follicular Carcinomas During the period 1972-1995, the secular trends for papillary carcinoma in Los Angeles County by sex show a distinct pattern of overall increase in incidence, particularly for females (Figure 10). Rates were low in the 1970’s, but begin to increase in the 1980’s. The age-adjusted incidence rate for females was highest in 1993 at 6.28 per 100,000 (95% C.I. 5.57-7.00). Rates for women were 2-3 times greater than those for men during the entire time period. The incidence rates for papillary carcinoma in males since 1972 remained relatively consistent, with only a slight overall increase in incidence over time. The highest incidence rate is evident in 1992 at 2.51 per 100,000 (2.01-3.01). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. In contrast, the secular trends for follicular carcinoma for both genders show an overall slight decrease in incidence since 1972 (Figure 10). The highest age-adjusted incidence rate for males was seen in 1974 at 0.59 per 100,000 (95 C.I. 0.33-0.84), while the highest rate for women was demonstrated in 1980 at 1.23 per 100,000 (95% C.I. 0.88- 1.58). 3.11 Medullary and Anaplastic Carcinomas Table 4 shows the age-adjusted incidence rates for medullary and anaplastic carcinomas in Los Angeles County between 1972-1995. Rates were low in both genders for these two types of histologies. For medullary carcinoma, rates were higher in females than in males at 0.17 per 100,000 (95% C.I. 0.14- 0.19) and 0.12 per 100,000 (95% C.I. 0.10-0.14), respectively. Medullary carcinoma accounted for only 3.2% (282 cases) of all invasive thyroid cancer cases during the 23- year period. Among males, those in “other” racial/ethnic groups (mostly Asian subgroups) had the highest incidence rate compared to the other ethnicities at 0.21 per 100.000 (95% C.I. 0.00-0.44) followed by non-Spanish sumamed whites at 0.14 per 100.000 (95% C.I. 0.10-0.17). Chinese females demonstrated the highest incidence rate at 0.32 per 100,000 (95% C.I. 0.05-0.59). Blacks showed equal rates of medullary carcinomas for both genders. Anaplastic carcinoma represented only 2 .1 % (1 8 5 cases) of the total invasive thyroid cancer cases. Overall, females showed higher rates th a n males at 0 .1 1 per 100.000 (95% C.I. 0.09-0.13) and 0.07 per 100,000 (95% C.I. 0.06-0.09), respectively. Rates were highest in Spanish sumamed males and females at 0.10 per 100,000 (95% C.I. 24 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.03-0.17) and 0.15 per 100,000 (95% C.I. 0.08-0.22), respectively. Japanese females showed the second highest incidence rate at 0.14 per 100,000 (95% C.I. 0.00-0.30). Chinese males and females had comparable rates to Spanish sumamed whites. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER IV DISCUSSION The pattern of thyroid cancer incidence in Los Angeles County is consistent with the general descriptive epidemiology established for this disease. Incidence is higher in women than in men and the age-adjusted incidence rates for women are more than twice the rates for men in each major ethnic group. Papillary carcinoma accounted for the majority of thyroid cancers in both men and women, followed by follicular, medullary, and anaplastic carcinoma. Papillary carcinoma is also more predominant among whites than blacks, while follicular carcinoma accounts for a higher proportion of cases in blacks than in whites. The age-specific incidence rates for papillary carcinoma followed a typical distribution, with women showing a rapid increase in incidence during puberty and reproductive years, which leveled off after menopause. Men demonstrated a more gradual increase in papillary carcinoma incidence rates with age. The age-specific distributions of follicular carcinoma showed similar patterns of increasing incidence with age for both genders. The incidence of medullary and anaplastic carcinomas was low among all ethnicities. 4.1 Incidence in Filipinos The Filipino population in Los Angeles County showed remarkably high incidence rates of thyroid cancer. This ethnic group demonstrated the highest incidence rates in both sexes for all invasive thyroid cancers, papillary carcinoma, and for follicular carcinoma in women. High thyroid cancer rates in Filipinos were first noted in Los 26 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Angeles County during the 1970’s (Preston-Martin and Menck, 1979) and have also been demonstrated in Hawaii (Goodman et al, 1988; Kolonel et al, 1990). 4.1.2 Migration A possible explanation for the marked elevation among Filipinos may be offered after comparing incidence rates in immigrants to the United States and the rates in the country of origin of this group. A recent study found that papillary carcinoma was twice as common am ong foreign-born Filipino men as among U.S. bom Filipino men. In women, elevated thyroid cancer rates were found in those who were Philippine-bom compared with both U.S. bom Filipino women and with U.S. bom white women for both papillary and follicular carcinoma (Rossing et al., 1995). The age-adjusted incidence rates of thyroid cancer reported in Manila, Philippines between 1983-1987 are 3.5 per 100,000 in males and 8.6 per 100,000 in females (Parkin et al., 1993). In Rizal Province, the rates were slightly lower at 2.1 per 100,000 in males and 7.7 per 100,000 in females. These rates are lower than rates reported here among Filipinos residing in Los Angeles County. The marked excess of papillary carcinoma in Filipino men and papillary and follicular carcinoma in Filipino women are consistent with the findings among Filipinos in Los Angeles County. The Filipino population in Los Angeles County has been increasing rapidly, comprising less than 50,000 persons in 1970 to almost 220,000 in 1990, which accounted for 2.5% of the county population overall in that year (Bernstein et al., 1995). Furthermore, 72.7% of the Los Angeles County Filipino population is foreign-born, with the majority emigrating from the Philippines. 27 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4.1.3 Dietary Factors - Tndine Intake The difference in incidence among the ethnic groups and the elevated incidence rates among Filipinos may be attributable to variations in diet. The roles of both iodine deficiency and iodine excess have been investigated as potential risk factors for thyroid cancer. Many areas that are characterized by a high incidence of thyroid cancer tend to be island populations that are characterized by high levels of iodine intake through seafood consumption, such as the island populations of Hawaii and Iceland. Thyroid cancer incidence rates are also reported to be high in the Pacific Islands o f New Caledonia, French Polynesia, Fiji, and Hawaii (Blot et al., 1997). Seafood consumption among Hawaiian men and women in certain age groups is more than 50 percent greater than for the general U.S. population (Kolonel et al., 1990). In contrast, some areas of endemic goiter and iodine deficiency also have excess thyroid cancer (Langsteger et al., 1993; Petterson et al., 1996). It has been postulated that iodine excess is associated with an increased risk of papillary carcinoma, whereas iodine deficiency is linked to follicular and anaplastic carcinomas. Several regions, such as Switzerland, Argentina, and the U.S. showed an increase in the incidence of papillary carcinoma following iodine supplementation (Wynder, 1952; Harach et al, 1985; Beahrs et al, 1951). In addition, areas where the population is characterized by high iodine intake, such as the islands of Japan, Hawaii, and Iceland, also have a higher incidence of papillary carcinoma, whereas areas with low iodine consumption, such as Columbia and Scotland, typically have higher frequencies of follicular carcinoma (Langsteger et al, 1993; Kolonel et al, 1990). 28 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A large number of migrants from the Philippines to the U.S. moved from northern Luzon, a region associated with endemic goiter (Kelly and Snedden, 1960; Kolonel, 1985). Since Filipino women in Los Angeles County have elevated incidence rates for both papillary and follicular carcinomas, further research is necessary to understand the reasons for this excess, for example to determine whether it can be attributed to the origins of Los Angeles Filipinos in endemic goiter areas in the Philippines or the seafood (and thus high iodine) intake in an island environment. 4.1.4 Dietary Factors - Goitrogenic Vegetables The consumption of goitrogenic vegetables may also play a role in the incidence of thyroid cancer among Filipinos. A recent study conducted in Hawaii found that Filipinos consumed more goitrogenic vegetables such as cabbage and turnips (Goodman et al., 1988). Goitrogens, discussed earlier, are thought to promote carcinogenesis via a mechanism similar to iodine deficiency in which a reduction in thyroid hormone levels occurs (Franceschi et al., 1991). Epidemiologic studies of goitrogenic vegetables, however, have shown equivocal results, which has been suggested to be due to the overlap of goitrogenic vegetables with the protective cruciferous vegetables that act to inhibit carcinogenesis (Kolonel et al., 1990). Studies have also shown that elevated levels of TSH and abnormal thyroid conditions tend to occur in areas characterized by both endemic goiter and high consumption of goitrogenic vegetables (Franceschi et al., 1990; McLaren and Alexander, 1979). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4.1.5 Volcanoes The role of exposure to volcanic activity in thyroid cancer incidence has also been investigated, mostly due to the increased thyroid cancer rates in areas with active volcanoes such as Hawaii and Iceland. These volcanoes, which are also present in the Philippines, produce basaltic lava and are thought to contain carcinogenic agents (Kung et al., 1981). 4.1.6 Benign Thvroid Diseases A history of other nonmalignant thyroid diseases, in addition to goiter, is a prime risk factor for thyroid cancer. It would be of interest to investigate whether Filipinos, in particular, are characterized by higher rates of thyroid diseases such as benign thyroid nodules, goiter, thyrotoxicosis and Hashimoto’s thyroiditis. 4.2 Reproductive Factors The high incidence of thyroid cancer among women has been hypothesized to be a result of elevated TSH (thyroid-stimulating hormone) levels that occur during puberty, pregnancy, and delivery and with the use of oral contraceptives. Increased levels of TSH are associated with thyroid growth, cell proliferation, and are hypothesized to ultimately increase risk of thyroid cancer (Preston-Martin et al., 1987). 4.2.1 Parity Several studies have shown an association between parity and thyroid cancer (Preston-Martin et al., 1987; Preston-Martin et al., 1993; Ron et al., 1987; McTieman et al., 1984b). This association is believed to be due to the gradual growth of the thyroid gland throughout pregnancy and a resulting rise in TSH production (Glinoer et al., 1990). 30 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Thyroid volume has been shown to increase as much as 30% from early pregnancy to delivery (Burrow, 1993). Some studies have found an increasing risk for thyroid cancer with increasing number of pregnancies (Ron et al., 1987; Preston-Martin et al., 1987). Other studies have not shown an increased risk for thyroid cancer in parous compared to non-parous women or with increasing number of pregnancies (Kolonel et al., 1990; Akslen et al., 1992; Galanti et al., 1996). An increased risk for thyroid cancer associated with miscarriage, particularly as an outcome of a first pregnancy, has also been shown (Preston-Martin et al., 1987; Preston-Martin et al., 1993; Ron et al., 1987; Kolonel et al., 1990), but these results have not been consistent. Miscarriage may be an indicator of underlying thyroid disease (Preston-Martin et al., 1987). 4.2.2 Menarche Some research has also found that women who experienced an earlier onset of menarche and regular menstrual cycles are at a lower risk for thyroid cancer (Ron et al., 1987), however, most studies have not found such associations (Preston-Martin et al., 1987; McTieman et al., 1987). A prospective cohort study of about 63,000 Norwegian women found that a long reproductive period, namely, early menarche and late menopause, was associated with an increased risk of papillary carcinoma and a decreased risk of follicular carcinoma (Akslen et al., 1992). 4.2.3 Menopause An increased risk of thyroid cancer has been shown in women with a history of artificial menopause (Galanti et al., 1996; Kolonel et al., 1990). The case-control study in 31 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Connecticut, however, did not find such an association (Ron et al., 1987). In Shanghai, more cases than controls experienced natural menopause (Preston-Martin et al., 1993). 4.2.4 Exogenous Hormones Studies of the relationship between thyroid cancer and the use of oral contraceptives and other exogenous hormones have shown mixed results. Some studies have shown increased risk for thyroid cancer in women with prior use of oral contraceptives (Ron et al., 1987; McTieman et al., 1984b; Preston-Martin et al., 1987; Preston-Martin et al., 1993). The mechanism believed to cause the increase in risk is the slightly elevated TSH levels in women on oral contraceptives compared to women on normal menstrual cycles (Weeke et al., 1975). The study in Washington found a significant increased risk for papillary carcinoma in women with past use of noncontraceptive estrogens, but no association was found for follicular carcinoma (McTieman et al., 1984b). A more recent study, however, found no association of use of oral contraceptives or hormone replacement therapy with risk of papillary carcinoma (Rossing et al., 1998). Finally, Levi et al. (1990) offer an additional explanation regarding the elevated thyroid cancer incidence rates among females; they suggest that women are more likely to “report small masses of the neck and/or nonspecific symptoms (e.g. fatigue, weight changes, etc.), as compared to their male counterparts, which may induce or anticipate the evaluation of thyroid function.” The influence of hormonal and reproductive factors in the etiology o f thyroid cancer warrants further study as a result of these inconsistencies. 32 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4-3 Secular Trends The secular trend described for Los Angeles County between 1972-1995 may be explained, in part, by applying a birth cohort analysis to those who were exposed as children to the wide use o f radiation treatment for benign head and neck conditions between 1920 and 1960. Despite the fact that no conclusive evidence has been established as to the link between the use of exogenous hormones and an increased risk of thyroid cancer, the more pronounced increase in incidence in women since 1972 in Los Angeles County, as compared to males, poses an interesting direction for future research. It is possible that the increase in incidence in women may be a result of the growth in popularity of the usage of oral contraceptives, artificial menopause, hormone replacement therapy and other hormonal factors. The overall increase in thyroid cancer incidence in Los Angeles County over the 23-year period may also be due to improved diagnostic tools such as thyroid scintigraphy, ultrasonography, and fine needle aspiration (Correa and Chen, 1995). Incidence rates for thyroid cancer are also influenced by occult thyroid carcinomas, particularly papillary carcinomas, which are frequently found at autopsy. In several autopsy studies, the prevalence o f papillary carcinoma ranged from 6% to over 20%. Changes in diagnostic methods can, therefore, lead to large changes in the number of detected cases and in the observed ratio of the different types of thyroid carcinomas (Williams, 1983). The increase in papillary carcinoma and the decrease in follicular carcinomas may also be due, in part, to the changes in classification of these two histologies in recent 33 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. decades. During this time, endemic goiter was more prevalent in many areas and pathologists recognized that follicular carcinoma was morphologically comparable to nodules or adenomas of the nodular adenomatous endemic goiter. As a result of interventions and the subsequent decrease o f endemic goiter, the frequency o f follicular and anaplastic carcinomas has decreased as well, while the frequency of papillary carcinomas has increased (Correa and Chen, 1995). In addition, the current and recognized mode of classification includes dividing these two histologies by their mode of progression and nuclear morphology, as opposed to the presence of papillae or follicles, which has resulted in some follicular carcinomas being classified as papillary (Pettersson et al., 1991). This change in classification, however, has not been consistent. Because some pathologists still apply the original classification system, there may still be some misclassification between papillary and follicular carcinomas (Correa and Chen, 1995). 4.4 Socioeconomic Status and Occupation There was a direct relationship of increasing incidence with increasing socioeconomic status among non-Spanish sumamed whites. The results for the other ethnic groups did not show any clear trends. The occupational data in Los Angeles County showed associations with primarily white-collar occupations. The excess proportional incidence of thyroid cancer seen in radiologic technicians is of particular interest, as this result is consistent with previous findings of increased risks in occupations associated with x-ray exposure (Hallquist et al., 1993; Wingren et al., 1995). The greater than expected number of thyroid cancer cases 34 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. seen in women who worked in sales, however, was inconsistent with the results seen in Shanghai women, where more controls than cases were found to work in sales. Despite this result, more Shanghai cases than controls worked in professional/technical occupations (Preston-Martin et al., 1993). Generally, the patterns for occupation in Los Angeles County were consistent with other studies that showed some increased risk among those in white collar occupations, such as teachers, dentists, and pharmacists; however, previous studies have not demonstrated social class or education as a risk factor for thyroid cancer (Kolonel et al., 1990; Ron et al., 1987; McTieman et al., 1984b). In Hawaii, the highest rates of thyroid cancer are found in Filipinos and Hawaiians, who rank lowest in socioeconomic indicators (Wegner et al., 1982), while Japanese and whites who are characterized by a higher socio-economic status, have lower rates of thyroid cancer (Goodman et al., 1988). In Los Angeles County, as discussed earlier, Filipinos have the highest incidence rates of thyroid cancer. It is important to recognize that the results for socioeconomic status, however, have a potential to be confounded by ethnicity. Goodman et al. (1988) suggest that the trend o f high cancer incidence with low socioeconomic status in Hawaii may be due to poor nutrition, health, and greater alcohol consumption. Furthermore, the lower incidence of thyroid cancer among blacks than in whites in the United States, which is also characteristic to Los Angeles County may be due to inadequate access to health care and, consequently, a smaller chance of diagnosing thyroid tumors (Correa and Chen, 1995). It is possible, therefore, that the pattern seen in Los Angeles County of higher incidence rates among higher socioeconomic status groups may be due to a detection 35 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. bias. This group may have a greater tendency and opportunity to seek medical care than other individuals. This hypothesis is supported by the finding o f over 20% o f papillary carcinomas being detected at autopsy (Williams, 1983). It can be assumed that a significant proportion of “hidden” papillary carcinomas cases are not detected before death, due to lack of medical attention among the lower socioeconomic groups. Therefore, if proper medical attention been rendered, these hidden cases would have been reported earlier and, presumably, weakened the linear trend of high incidence rates in high socioeconomic groups. It is interesting to note that among the male cases of thyroid cancer found in Hawaii, eight of the nine cases among farm laborers were Filipino compared to one of the four controls. Work as a farm laborer was significantly associated with risk in Filipino men. This occupation is characterized by frequent exposure to chemical pesticides and herbicides, which have been linked to thyroid cancer. In addition, of all the ethnic groups in Hawaii, Filipinos had the highest proportion employed as farm laborers (Kolonel et al., 1990). The case-control study conducted in Shanghai (Preston-Martin et al., 1993) also found that all four of its cases in an agriculture/animal husbandry occupational category worked as vegetable farmers, suggesting chemical exposure. 4.5 Conclusions Further research needs to be extended to determine the exact role of iodine, diet, prior thyroid disease and hormonal and reproductive factors in thyroid cancer incidence. The descriptive epidemiology of thyroid cancer in Los Angeles County is likely to result from a combination of these factors, but other as yet unrecognized etiologic factors may 36 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. also play a role. Additional studies of the epidemiologic characteristics of the Filipino population in Los Angeles County are necessary to determine whether the increased incidence among this group is due to environmental, biological, or occupational exposures. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. REFERENCE LIST American Cancer Society-Thyroid Cancer Information. http://www.cancer.org/cidSpecificCancers/thyroid/index.html Beahrs OH, Pemberton JD, Black BM. Nodular goiter and malignant lesion of the thyroid gland. J Clin Endocrinol 1951; 11: 1157. Bernstein L, Miu A, Henderson BE, Ross RK. Cancer incidence among Filipinos in Los Angeles County, 1972-1991. Int J Cancer 1995; 63: 345-348. Blair A, Stewart PA, Tolbert PE, Grauman D, Moran FX, Vaught J, Rayner J. Cancer and other causes of death among a cohort of dry cleaners. Br J Indust Med 1990; 47: 162-168. Bleuer JP, Averkin YI, Abelin T. Chernobyl-related thyroid cancer: What evidence for role of short-lived iodines? Environ Health Perspect 1997; 105: 1483-1486. Blot WJ, Le Marchand LL, Boice JD Jr., Henderson BE. Thyroid Cancer in the Pacific. J Nat Cancer Inst 1997; 89: 90-91. Boring CC, Squires TS, Tong T. Cancer statistics. CA Cancer J Clin 1994; 44: 7-26. Breslow NE, Enstrom JE. Geographic correlations between cancer mortality rates and alcohol-tobacco consumption in the United States. J Natl Cancer Inst 1974; 53: 631-639. Burrow GN. Thyroid function and hyperfunction dining gestation. Endocrine Reviews 1993; 14: 194-202. Caldwell GG, Kelley D, Zack M, Falk H, Heath CW. Mortality and cancer frequency among military nuclear test (smoky) participants, 1957 through 1979. JAMA 1983; 250: 620-624. Carstensen JM, Wingren G, Hatschek T, Fredriksson M, Noorlind-Brage H, Axelson O. Occupational risks of thyroid cancer: Data from the Swedish Cancer Environment Register, 1961-1979. Am J Indust Med 1990; 18: 535-540. Conard RA. Late radiation effects in Marshall Islanders exposed to fallout 28 years ago. In: Boice JD Jr, Fraumeni JF Jr, eds. Radiation Carcinogenesis: Epidemiology and biological significance. New York: Raven Press 1984; 57-71. Correa P, Chen VW. Endocrine gland cancer. Cancer 1995; 75: 338-352. 38 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. D’Avanzo B, La Vecchia C, Franceschi S, Negri E, Talamini R. History of thyroid diseases and subsequent thyroid cancer risk. Cancer Epidemiology Biomarkers Prev 1995; 4: 193-199. Doniach I. Aetiological considerations of thyroid cancer. Br J Radiol 1971; 44: 819. Duffy BJ Jr, Fitzgerald PJ. Cancer of the thyroid in children: A report of 28 cases. J Clin Endocrinol Metab 1950; 10: 1296-1308. Franceschi S, Levi F, Negri E, Fassina A, La Vecchia C. Diet and thyroid cancer: A pooled analysis of four European case-control studies. Int J Cancer 1991; 48: 395-398. Franceschi S, Talamini R, Fassinia A, Bidoli E. Diet and epithelial cancer of the thyroid gland. Tumori 1990; 76: 331-338. Franssila K, Saxen E, Teppo L, Bjamason H, Tulinius H, Normann T, Ringertz N. Incidence of different morphological types of thyroid cancer in the Nordic countries. Acta Path Microbiol Scand 1981; 89: 49-55. Galanti MR, Hansson L, Lund E, Bergstrom R, Grimeiius L, Stalsberg H, Carlsen E, Baron JA, Persson I, Ekbom A. Reproductive history and cigarette smoking as risk factors for thyroid cancer in women: A population-based case control study. Cancer Epidemiology Biomarkers Prev 1996; 5:425-431. Galanti MR, Sparen P, Karlsson A, Grimeiius L, Ekbom A. Is residence in areas of endemic goiter a risk factor for thyroid cancer? Int J Cancer 1995; 61: 615-621. Glinoer D, De Nayer P, Bourdoux P, Lemone M, Robyn C, Van Steirteghem A, Kintheart J, Lejeune B. Regulation of maternal thyroid during pregnancy. J Clin Endocrinol Metab 1990; 276-287. Goodman MT, Yoshizawa CN, Kolonel LN. Descriptive epidemiology of thyroid cancer in Hawaii. Cancer 1988; 61:1272-1281. Grimalt JO, Sunyer J, Moreno V, Amaral OC, Sala M, Rosell A, Anto JM, Albaiges J. Risk excess of soft-rissue sarcoma and thyroid cancer in a community exposed to airborne organochlorinated compound mixtures with a high hexachlorobenzene content. Int J Cancer 1994; 56: 200-203. Hallquist A, Hardell L, Degerman A, Boquist L. Occupational exposures and thyroid cancer: Results of a case-control study. Eur J Cancer Prev 1993; 2: 345-349. Harach HR, Franssila KO, Wasenius V-M. Occult papillary carcinoma of the thyroid. Cancer 1985; 56: 531-538. 39 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Kazakov VS, Demidchik EP, Astakhova LN. Thyroid cancer after Chernobyl. Nature 1992; 359: 21. Kelly FC, Snedden WW. Prevalence and geographical distribution of endemic goiter. In: Endemic Goiter. Geneva, Switzerland: World Health Organization, 1960; Monogr. Series No. 44. Koionel LN. Cancer incidence among Filipinos in Hawaii and the Philippines. NCI Monogr 1985; 69: 93-8. Koionel LN, Hankin JH, Wikens LR, Fukunaga FH, Hinds MW. An epidemiologic study of thyroid cancer in Hawaii. Cancer Causes Control 1990; 1: 223-234. Kung TM, Ng WL, Gibson JB. Volcanoes and carcinoma of the thyroid: A possible association. Arch Env Health 1981; 36: 265-7. Langsteger W, Koltringer P, Wolf G, Dominik K, Buchinger W, Binter G, Lax S Eber O. The impact of geographical, clinical, dietary and radiation-induced features in the epidemiology of thyroid cancer. Eur J Cancer 1993; 29 A: 1547-1553. Levi F, Franceschi S, Van-Cong T, Negri E, La Vecchia C. Descriptive epidemiology of thyroid cancer in the Swiss Canton of Vaud. J Cancer Res Clin Oncol 1990; 116: 639- 647. Liu L, Deapen D, Bernstein L. Socioeconomic status and cancer of the female breast and reproductive organs: A comparison across racial/ethnic populations in Los Angeles County, California (United States). Cancer Causes Control, in press. Lundell M, Hakulinen T, Holm L-E. Thyroid cancer after radiotherapy for skin hemangioma in infancy. Radiation Res 1994; 140: 334-339. McCance KL, Huether SE. Pathophysiology, The Biologic Basis for Disease in Adults and Children. St. Louis: The C.V. Mosby Company 1990; 574-577. McLaren EH, Alexander WD. Goitrogens. Clin Endocrinol Metab 1979; 8: 129-144. McTieman AM, Weiss NS, Daiing JR. Incidence of thyroid cancer in women in relation to previous exposure to radiation therapy and history of thyroid disease. J Natl Cancer Inst 1984a; 73: 575-581. McTieman AM, Weiss NS, Daiing JR. Incidence of thyroid cancer in women in relation to reproductive and hormonal factors. Am J Epid 1984b; 120:423-435. 40 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. McTieman AM, Weiss NS, Daiing JR. Incidence of thyroid cancer in women in relation to known or suspected risk factors for breast cancer. Cancer Res 1987; 47:292-295. National Academy of Sciences, Committee on Diet, Nutrition, and Cancer. Diet, nutrition, and cancer: Interim dietary guidelines. JNCI 1983; 70: 1151-1170. Negri E, La Vecchia C, Franceschi S, D’Avanzo B, Parazzini F. Vegetable and fruit consumption and cancer risk. Int J Cancer 1991; 48: 350-354. Parkin DM, Muir CS, Whelan SL, Gao YT, Ferlay J, Powell J. Cancer Incidence in Five Continents. Vol. 6. Lyon, France: International Agency for Research on Cancer, 1993; IARC Sci. Pub. No. 120. Pendergrast WJ, Milmore BK, Marcus SC. Thyroid cancer and thyrotoxicosis in the United States: Their relation to endemic goiter. J Chron Dis 1961; 13: 22-38. Pesatori AC, Consonni D, Tironi A, Zocchetti C, Fini A, Bertazzi PA. Cancer in a young population in a dioxin-contaminated area. Int J Epid 1993; 22: 1010-1013. Petterson B, Adami H-O, Wilander E, Coleman MP. Trends in thyroid cancer incidence in Sweden, 1958-1981, by histopathologic type. Int J Cancer 1991; 48: 28-33. Petterson B, Coleman MP, Ron E, Adami H-O. Iodine supplementation in Sweden and regional trends in thyroid cancer incidence by histopathologic type. Int J Cancer 1996; 65:13-19. Preston-Martin S, Bernstein L, Pike MC, Maldonado AA, Henderson BE. Thyroid cancer among young women related to prior thyroid disease and pregnancy history. Br J Cancer 1987; 55: 191-195. Preston-Martin S, Jin F, Duda MJ, Mack WJ. A case-control study of thyroid cancer in women under age 55 in Shanghai (People’s Republic of China). Cancer Causes Control 1993; 4: 431-440. Preston-Martin S, Menck HR. The epidemiology of thyroid cancer in Los Angeles County. West J Med 1979; 131: 369-372. Prisyazhiuk A, Pjatak O, Buzanov VA, Reeves Fk, Beral V. Cancer in Ukraine, post- Chernobyl. Lancet 1991; 338: 1334-1335. Purves WK, Orians GH, Heller HC. Life, The Science of Biology. Massachusetts: Sinauer Associates, Inc. 1992; 775-777. 41 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ron E. Thyroid cancer. In: Cancer Epidemiology and Prevention. Schottenfeld and Fraumeni eds. New York: Oxford University Press 1996; 1000-1021. Ron E, Kleinerman RA, Boice JD Jr, LiVolsi VA, Flannery JT, Fraumeni JF Jr. A population-based case-control study of thyroid cancer. J Natl Cancer Inst 1987; 79: 1-12. Ross RK, Bernstein L, Hartnett NM, Boone JR. Cancer patterns among Vietnamese immigrants in Los Angeles County. Br J Cancer 1991; 64: 185-186. Rossing MA, Schwartz SM, Weiss NS. Thyroid cancer incidence in Asian migrants to the United States and their descendants. Cancer Causes Control 1995; 6:439-444. Rossing MA, Voigt LF, Wicklund KG, Williams M, Dalin JR. Use o f exogenous hormones and risk of papillary thyroid cancer (Washington, United States). Cancer Causes Control 1998; 9: 341-349. Saracci R, Kogevinas M, Bertazzi P-A, Bueno de Mesquita BH, Coggon D, Green LM, Kauppinen T, L’Abbe KA, Littorin M, Lynge E, Mathews JD, Neuberger M, Osman J, Pearce N, Winkelmann R. Cancer mortality in workers exposed to chlorophenoxy herbicides and chlorophenols. Lancet 1991; 338: 1027-1032. Schimke RN, Hartmann WH, Prout TE, Rimoin DL. Syndrome of bilateral pheochromocytoma, medullary carcinoma and multiple neuromas. N Engl J Med 1968; 279: 1-7. Schneider AB, Ron E, Lubin J, Stovall M, Gierlowski TC. Dose-response relationships for radiation-induced thyroid cancer and thyroid nodules: Evidence for the prolonged effects of radiation on the thyroid. J Clin Endocrinol Metab 1993; 77: 362-369. Shore RE, Woodard E, Hildreth N, Dvoretsky P, Hempelmann L, Pasternack B. Thyroid tumors following thymus irradiation. J Natl Cancer Inst 1985; 74: 1177-1184. Thompson DE, Mabuchi K, Ron E, Soda M, Tokunaga M, Ochikubo S, Sugimoto S, Ikeda T, Terasaki M, Izumi S, Preston DL. Cancer incidence in atomic bomb survivors, Part II: Solid tumors, 1958-1987. Radiation Res 1994; 137: S17-S67. Weeke J, Hansen AP. Serum TSH and serum T3 levels during normal menstrual cycles and during cycles on oral contraceptives. Acta Endocrinol 1975; 431-438. Wegelin C. Malignant disease o f the thyroid gland and its relation to goitre in man and animal. Cancer Rev 1928; 3: 297-313. 42 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Wegner EL, Koionel LN, Nomura AMY, Lee J. Racial and socio-economic status differences in survival o f colorectal cancer patients in Hawaii. Cancer 1982; 49: 2208- 2216. Williams ED. The aetiology of thyroid tumors. Clin Endocrinol Metab 1979; 8: 193- 207. Williams ED. Epidemiology and genetic factors in thyroid carcinoma. Acta Endocrinol 1983; Supp 252: 11-12. Williams ED, Doniach I, Bjamason O, Michie W. Thyroid cancer in an iodine-rich area: A histopathological study. Cancer 1977; 39: 215-222. Williams RR. Breast and thyroid cancer and malignant melanoma promoted by alcohol- induced pituitary secretion of prolactin, TSH and MSH. Lancet 1976; 2: 456. Wingren G, Hallquist A, Degerman A, Hardell L. Occupation and female papillary cancer of the thyroid. J Occup Environ Med 1995; 37: 294-297. Wynder El. Some practical aspects of cancer prevention (concluded). N Engl J Med 1952; 246:573-582. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 1. Average Annual Age-Adjusted Incidence Rates, Median Age at Diagnosis, and 5-Year Relative Survival Rate of Thyroid Cancer, by Histologic Type, SEER, 1973-87* Characteristic Papillary Follicular Medullary Anaplastic Age-adjusted incidence rate (per 100,000)+ White Male 1.6 0.4 0.1 0.1 Female 4.2 0.9 0.2 0.1 Black Male 0.7 0.4 0.1 0.0 Female 2.1 1 2 0.1 0.1 Median age at diagnosis 41 50 51 71 5-year survival rate (%) (all stages) 98.1 92.0 81.8 8.0 Source: SEER: Surveillance, Epidemiology, and End Results (Correa and Chen, 1995) •Microscopically confirmed cases only. "Rates standardized to the 1970 U.S. population distribution Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 2. Occupations Showing Elevated* Proportional Incidence Ratios (PIR) for Thyroid Cancer in Non-Spanish Snrnamed Whites, Los Angeles County, 1972-1995 MALES FEMALES Occupation leases PIR 95% C J. #cases PIR 95% CJ. Lawyers 29 156.2 (104.6-224.4) 18 133.1 (78.8-210.3) Dentists 12 388.4 (200.5-678.5) 1 126.0 (1.6-701.3) Pharmacists 6 294.4 (107.5-640.9) 1 99.6 (1.3-553.9) Physicians 34 240.6 (166.6-336.2) 12 164.6 (85.0-287.6) Radiologic technicians 5 425.8 (137.2-993.6) 4 113.6 (30.6-290.8) Economists 8 239.8 (103.2,472.5) 9 126.1 (57.5-239.4) Psychologists 8 349.7 (150.6-689.0) 13 220.1 (117.1-376.3) Teacher, college & univ. 12 250.4 (129.2-437.4) 7 95.1 (38.1-196.0) Musicians & composers 12 200.2 (103.3-349.8) 4 80.9 (21.8-2072) Managers & admin. 187 116.9 (100.8-134.9) 129 95.0 (79.3-112.9) Salesmen 3 105.4 (21.2-307.9) 9 240.3 (109.7-456.3) Bookkeepers 0 — — 6 331.2 (120.9-720.9) Stenographers 0 — — 9 232.6 (106.1-441.6) Homemakers 3 307.1 (61.7-897.3) 813 110.2 (102.7-118.0) ’ Confidence interval excludes 100 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3. Distribution of Thyroid Cancer Cases by Ethnic Group, Histologic Type, and Sex in Los Angeles County, 1972-1995__________________________________________________________ No. of cases (percent) Males-Histologic Type Ethnic Group Papillary Follicular Medullary Undifferentiated Other Non-Spanish Sumamed White 1180 (72) 263 (16) 76(5) 39(2) 76(5) Spanish Sumamed White 260 (74) 46(13) 20(6) 11(3) 13(4) Black 73 (60) 28 (23) 7(6) 4(3) 10(8) Filipino 59 (88) 5(7) 1(1) K D KD Korean 12 (86) 1(7) 1(7) 0(0) 0(0) Japanese 24 (83) 3(10) 0(0) 0(0) 2(7) Chinese 32 (82) 4(10) 1(3) 2(5) 0(0) Other 26 (63) 8(20) 4(10) 3(7) 0(0) Total 1666 (72) 358(15) 110(5) 60(3) 102 (4) Females-Histologic Type Ethnic Group Papillary Follicular Medullary Undifferentiated Other Non-Spanish Sumamed White 3085 (76) 572(14) 125 (3) 89 (2) 179(4) Spanish Sumamed White 1097 (80) 185(14) 29(2) 18(1) 43 (3) Black 271 (67) 94 (23) 7(2) 10(2) 20 (5) Filipino 242 (85) 29 (12) 1 (<D 1 (<1) 6(2) Korean 76 (89) 7(8) 1(1) 0(0) 3(4) Japanese 85 (82) 14(13) KD 3(3) K D Chinese 88 (81) 9(8) 6(6) 2(2) 4(4) Other 11 1 (79) 19(14) 2(1) 2(1) 6(4) Total 5018(77) 929(14) 172 (3) 125 (2) 174(3) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 4. Average Annual Age-Ad justed Incidence Rates * (per 100,000) by Race - M edullary and Anaplastic Carcinomas, Los Angeles County, 1972-1995_________ Medullary Males 95% C.L Females 95% CJ. Non-Spanish Surnamed White 0.14(76)' (0.10-0.17) 0.20 (125) (0.16-0.24) Spanish Surnamed White 0.09 (20) (0.04-0.14) 0.16(29) (0.10-0.23) Black 0.06 (7) (0.02-0.11) 0.06 (7) (0.01-0.10) Filipino 0.07(1) (0.00-0.21) 0.09(1) (0.00-0.27) Korean 0.05 (1) (0.00-0.14) 0.06(1) (0.00-0.18) Japanese 0.00 (0) - 0.07(1) (0.00-0.20) Chinese 0.03 (I) (0.00-0.10) 0.32 (6) (0.05-0.59) Other 0.21 (4) (0.00-0.44) 0.05 (2) (0.00-0.13) All Races 0.12(110) (0.10-0.14) 0.17(172) (0.14-0.19) Anaplastic Males 95% CL Females 95% C.I. Non-Spanish Surnamed White 0.07 (39) (0.05-0.09) 0.10(89) (0.08-0.12) Spanish Surnamed White 0.10(11) (0.03-0.17) 0.15(18) (0.08-0.22) Black 0.05 (4) (0.00-0.11) 0.09 (10) (0.03-0.15) Filipino 0.09(1) (0.00-0.27) 0.07(1) (0.00-0.21) Korean — — — — Japanese 0.00 (0) — 0.14(3) (0.00-0.30) Chinese 0.10(2) (0.00-0.25) 0.13(2) (0.00-0.30) Other 0.23 (3) (0.00-0.50) 0.09 (2) (0.00-0.22) All Races 0.07 (60) (0.06-0.09) 0.11 (125) (0.09-0.13) * Rates standardized to the 1970 U.S. population distribution * Age-adjusted incidence rate (Number) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1. Average Annual Age-Adjusted Thyroid Cancer Incidence Rates by Sex and Ethnicity, Los Angeles County, 1972-1995 Non-Spanish Sumamed White Spanish Sumamed White Black Filipino Korean Japanese Chinese Other 0.00 2.00 4.00 6.00 8.00 10.00 12.00 ■ Females ■Males •Total c a se s, 1972-1995 A ge-adjusted incidence rate (per 100,000) Reproduced with permission o f th e copyright owner. Further reproduction prohibited without permission. Figure 2. Secular Trend in Thyroid Cancer Incidence by Sex, with Regression, Los Angeles County, 1972-1995 8.00 o o • t o o 6.00 k 0 > a $ 5.00 & a > C 4.00 o ■ o o .£ 3.00 ■ o £ (0 3 2.00 X J ¥ 0 ) o) i.oo 0.00 c M c o ^ - i n < o i ^ - c o o ) O T - c s ) c o ^ i n < o N . c o a > o * - ( \ j e o i ^ r ^ r ^ - h - t ^ h ' h ' h ~ o o o o o o o o o o o o o o o o o o o o o > o ) O j a > 0 ) C J ) a ) 0 5 0 ) c n c n c D 0 ) 0 ) 0 > 0 > 0 ) 0 ) 0 > 0 ) 0 ) 0 ) 0 ) 0 ) 0 ) 0 > to o > o> Males • Females ■Linear (Females) ■Linear (Males) Year VO Reproduced with permission o f th e copyright owner. Further reproduction prohibited without permission. Figure 3. Age-Specific Thyroid Cancer Incidence Rates by Sex, All Races Combined, Los Angeles County, 1972-1995 14.00 12.00 o o 8.00 6.00 4.00 2.00 0.00 ? o > 9 T V O W O lO o > 9 o CM O ) CO i w c o o > 9 1 0 CM 3 o CO O ) O ) in ■ in in ? o > 9 o m co co o > 9 m + m o in o o o Age at diagnosis — a— Males Females Reproduced with permission o f th e copyright owner. Further reproduction prohibited without permission. Figure 4. Average Annual Age-Adjusted Thyroid Cancer Incidence Rates by Socio Economic Status in Non-Spanish Surnamed Whites, Los Angeles County, 1972-1995 o o o 8.00 7.00 6.00 0 ) a 5.00 4.00 | 2 a > o c 0 •o 5 .5 3.00 •o 1 = 2.00 •o ? a a) < 1.00 0.00 High Mid-to-High Mid-Range Mid-to-Low Socio-Economic Status Low ■ Males ■Females Figure 5. Distribution of Thyroid Cancer by Histologic Type, Los Angeles County, 1972-1995 Males (2311 cases) Papillary 72% (1666 cases) Females (6509 cases) Anaplastic Other 1.9% 4.0% Medullary (125 cases) (262 cases) 2.6% X (172 cases) Follicular 14% ^ (929 cases) Papillary 77% (5018 cases) 52 Anaplastic Qther 2- 6% 4 .4% (60cases)(102cases) Medullary 4.8% (110 cases) Follicular 16% (358 cases) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission o f th e copyright owner. Further reproduction prohibited without permission. Figure 6. Average Annual Age-Adjusted Incidence Rates for Papillary Carcinoma by Race, Los Angeles County, 1972-1995 Non-Spanish Sumamed White Spanish Sumamed White Black * • M B o • B M C 5 U J Filipino Korean Japanese Chinese Other 0.00 l/l u > *Total c a s e s , 1972-1995 2.00 4.00 6.00 8.00 10.00 Age-adjusted incidence rate (per 100,000) 12.00 ■ Females ■ Males Reproduced with permission o f th e copyright owner. Further reproduction prohibited without permission. Figure 7. Age-Specific Incidence Rates, Papillary Carcinoma, Los Angeles County, 1972-1995 10.00 9.00 8.00 o o o * o o T ~ k . 0 > a 7.00 6.00 ® 5.00 1 ® 4.00 2 3.00 c 2.00 1.00 0.00 s I O ) o ■ m o c n t— C M i O 3 ■ o C O O ) C O O ) < 9 * 9 O lO ? ? 3 o in m - o O ) r> + m o o o o Age at diagnosis Males Females Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Figure 8. Average Annual Age-Adjusted Incidence Rates for Follicular Carcinoma by Race, Los Angeles County, 1972-1995 * 0 c 1 Non-Spanish Surnamed White Spanish Surnamed White Black Filipino Korean Japanese Chinese Other 0.00 •Total c a s e s , 1972-1995 0.20 0.40 0.60 0.80 1.00 1.20 Age-adjusted incidence rate (per 100,000) 1.40 ■ Females ■ Males Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Figure 9. Age-Specific Incidence Rates, Follicular Carcinoma, Los Angeles County, 1972-1995 2.50 2.00 o o © o h o a c 0 ) o c o T3 O e 1.00 0.50 0.00 o 0 0 + i n o > cm o > cm * 9 s O l O o o > i n ? a> < 9 o m < o c o O ) 3 * o CO CD CO O m CM CO Males ■ Females Age at diagnosis 1 f t O s Reproduced with permission o f th e copyright owner. Further reproduction prohibited without permission. Figure 10. Secular Trend in Papillary and Follicular Carcinoma, Los Angeles County, 1972-1995 8.00 © 7.00 3 C M t" . < 0 N - 00 h- o 00 C M 0 0 s to 00 0 0 0 0 o C J ) C M o s o > o > O ) O ) C J ) C D O ) C J ) O ) C D C D O ) T “ T - T “ r- r— Year T — T “ Males-Papillary — ■— Females-Papillary Males-Follicular Females-Follicular Linear (Females-Papillary) Linear (Males-Papillary) Linear (Females-Follicular) — Linear (Males-Follicular) IMAGE EVALUATION TEST TARGET (Q A -3 ) W V < ' < : /_ 1 .0 l.l 128 ■ 23 1 3 2 Z y& £ L° 1.25 m i l 1 .4 1 .8 1 .6 150mm V / ; V o / / j A P P L I E D A IIW IG E . In c 1653 East Main Street - = ~ - Rochester. N Y 14609 USA = Phone: 716/482-0300 - = ~ - = Fax: 716/288-5989 0 1 9 9 3 . A p p l i e d I m a g e . I n c .. A l l R i g h t s R e s e r v e d Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
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Descriptive epidemiology of thyroid cancer in Los Angeles County, 1972-1995
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