A "registry" of all known cases of nasopharyngeal carcinoma in Malaysia, 1968-72, was established. Attention was focused on the State of Selangor where conditions are best for case finding. Age-adjusted incidence rates among Chinese males and females were 17·3 and 7·3 per 100,000; among Malay males and females, the rates were 2·5 and 0·3 and among Indian males, 1·1. The detailed ethnicity of 192 cases in Selangor was established. Estimated incidence rates for the Chinese sub-groups agreed with the pattern observed elsewhere: highest among the Cantonese, lowest among the Hokkien/Teochiu, with the Khek in between. There was no correlation between histological type and sub-ethnic group among the Chinese cases.
Histocompatibility locus A typing of 43 Malaysian Chinese and 51 Hong Kong Chinese patients with nasopharyngeal carcinoma (NPC) confirmed the association between the occurrence of A2-Sin 2 and the increased risk for NPC that was previously demonstrated in Singapore Chinese. The results support the previous interpretation that the histocompatibility locus A genotype of importance in NPC predisposition is the A2-Sin 2 haplotype. The histocompatibility locus A-linked, genetically determined NPC risk is common to Asian Chinese from at least three geographic locations.
Incidence patterns indicated the prominent role of genetic factors in this type of cancer. A histocompatibility leukocyte antigen (HLA) profile of A2 and B-locus antigen, Singapore 2 (Sin 2), was identified. An association between these genes and increased risk for nasopharyngeal carcinoma (NPC), was confirmed. The risk was restricted to the "co-occurrence" of A2, B-Sin 2, suggesting that the genotype predisposing to the development of NPC was the A, B-Sin 2 haplotype. Similar associations were found to exist in Malaysian and Hong Kong Chinese so the A2, B-Sin 2 phenotype is a feature common to Asian Chinese in at least three locations. Preliminary HLA studies of medium NPC incidence in Tunisians and Malays indicated that patients with NPC of both ethnic types have altered HLA antigen profiles. If the findings of a locus-B antigen deficit in Tunisians and the role of A9 with B-locus antigens in Malays can be confirmed and clarified, the histocompatibility genetic hypothesis of NPC predisposition would be substantially strengthened.
Malaysia and Hawaii have several advantages for epidemiologic and laboratory studies on nasopharyngeal carcinoma. Both have multiethnic populations with different incidence rates of nasopharyngeal carcinoma and different life-styles. Malaysia has large populations of Chinese, Malaya, and Indians, and the number of cases of nasopharyngeal carcinoma at any one time is comparatively large. Incidence rates for 1968--72, age-standardized to the World population, for Guangdong hua (Cantonese Chinese) in Malaysia were 24.3/100,000 for males and 12.0/100,000 for females. In Hawaii, the ratio was 12.9/100,000 for males and 6.7/100,000 for females. The small number of cases in Hawaii would require that research in that State be conducted in collaboration with research elsewhere with larger case numbers.