High incidence of nasopharyngeal carcinoma in native people of Sarawak, Borneo Island.

ABSTRACT

Nasopharyngeal cancer (NPC) is generally a rare malignancy with a few well-known exceptions, notably South-East China. In this article, we describe evidence of a high risk of NPC in the population of Sarawak State, Malaysia, and particularly in one native ethnic group. Sarawak State is one of the two provinces of Malaysia located on the island of Borneo. The native population (71.6%) includes the Iban, Malay, Bidayuh, Melanau, and diverse smaller ethnic groups. The Chinese are the largest nonindigenous group (27.5%). We identified 392 newly diagnosed cases (292 males and 100 females) of NPC in 1996-1998 in Malaysian citizens, permanent residents of Sarawak. Age-standardized rates by sex and ethnic group were compared with the highest rates in the world. The age-adjusted rate (ASR) in Sarawak residents was 13.5/100,000 [95% confidence interval (CI) 12.2-15.0] and 6.2/100,000 (95% CI 5.7-6.7) in males and females, respectively. The risk in the Bidayuh people was 2.3-fold (M) and 1.9-fold (F) higher than the Sarawak average, and about 50% higher than that in Hong Kong-the highest recorded by any population-based registry for the same period. Local dietary habits, environmental exposures, and genetic susceptibility deserve investigation in this population.