Thyroid cancer in the Middle Eastern population of California.

ABSTRACT

OBJECTIVE: To describe and compare the epidemiology of thyroid cancer in the rapidly growing Middle Eastern (ME) population and the non-Hispanic, non-Middle Eastern White (NHNMW) residents of California. Population with ME heritage that is officially not recognized as a distinct ethnicity has rarely been studied in the past. METHODS: ME cases in the California cancer registry files for 1988-2004 were identified by surname recognition. ME population was estimated by ancestry from census data. RESULTS: Thyroid cancer in ME group, 869 cases and 56 deaths were compared with 19,182 cases and 1,327 deaths in the NHNMW population. Age-adjusted rate ratio (RR) for incidence was 1.5 (95% CI 1.3-1.7) in men and 1.5 (95% CI 1.4-1.7) in women. RR for mortality was 1.4 (95% CI 0.9-2.4) in men and 2.3 (95% CI 1.4-3.9) in women. Papillary tumors comprised over 80% of all cases and their pattern correlated with the rapid increase in thyroid cancer in recent years. Five-year observed survival in ME men was significantly higher than in NHNMW men, but similar in women. CONCLUSIONS: Eighty-five percent of ME cases identified in this study were born in the Middle East. The higher incidence of thyroid cancer in this immigrant population may largely reflect a combination of sequels of radiation treatment for fungal diseases of the scalp that was common in the area in early 1950s, benign proliferative thyroid disease that is common in the area due to dietary iodine imbalance, and possibly genetic predisposition.