Trends in the incidence rates of nasopharyngeal carcinoma among Chinese Americans living in Los Angeles County and the San Francisco metropolitan area, 1992-2002.

Nasopharyngeal carcinoma is much more common in Asian countries than in Western countries. However, since the 1980s, nasopharyngeal carcinoma incidence has fallen among both men and women in Hong Kong, and recently a similar trend has also been noted in Singapore. Using data from the Surveillance, Epidemiology, and End Results Program and the US Census, the authors evaluated recent trends in the incidence rates of nasopharyngeal carcinoma among Chinese living in Los Angeles County and in the San Francisco-Oakland (California) metropolitan area. From 1992 to 2002, the rates of nasopharyngeal carcinoma in these two populations decreased in men by 37% (95% confidence interval: -54, -12) but in women by just 1% (95% confidence interval: -40, 64). In Chinese men, the overall decline in incidence was limited primarily to a decline in the rate of type I tumors (differentiated squamous tumors with keratin production). While the reasons underlying the observed patterns of incidence remain to be determined, changes in lifestyle and environment are likely to be contributory factors.