Descriptive epidemiology of thyroid cancer in Los Angeles County, 1972-1995

Objective: To examine the descriptive epidemiologic features of incident thyroid cancers diagnosed among Los Angeles County residents between 1972 and 1995. Methods: The Los Angeles County/University of Southern California Cancer Surveillance Program (CSP) collected data on 8820 newly diagnosed thyroid cancer of cases occurring in Los Angeles County. Average annual age-adjusted incidence rates were calculated to study the epidemiology of each of the major histologic types of thyroid carcinoma. Results: For all races combined, the age-adjusted incidence rates were 2.5 per 100,000 males and 6.0 per 100,000 females. Differences in incidence by ethnicity were particularly striking, with Filipinos demonstrating the highest incidence rates (4.44 per 100,000 males, 11.3 per 100,000 females). Over the 23-year period, thyroid cancer incidence rates increased 1.5% per year for males and 1% per year for females. By histology, papillary carcinoma rates increased over time and follicular carcinoma rates decreased. Non-Spanish surnamed white men employed in certain white-collar occupations and radiologic technicians were at greater risk of thyroid cancer. Conclusions: Additional research on the epidemiologic risk factors for thyroid cancer, particularly for gender and ethnicity, is needed to explain the marked elevated incidence rates among females and the Filipino population in Los Angeles County.