The Singapore Cancer Registry started operations on January 1, 1968. It is a population-based registry that seeks to obtain basic epidemiological and clinical data on all cases of cancer diagnosed in Singapore. The results presented pertain only to Singapore citizens and permanent residents and cover the period from 1973 to 1977. Of special interest are the cancer patterns of the main ethnic groups in Singapore. Generally, the Chinese (76% of total population) have significantly higher risks for cancer; the most prevalent sites are the nasopharynx, esophagus, stomach, liver, and lung. Within the Chinese group are also dialect group differences. The Malays (15% of population) have the lowest rates for most sites, whereas among the Indians (7% of population), mouth cancer is an important site for both sexes. All these variations provide useful clues in the search for etiological factors.
The history of efforts to establish a cancer registry in Malaysia since 1961 is reviewed. In 1980, the staff of the Institute for Medical Research in Kuala Lumpur was authorized to develop an official registry that would combine the resources of the various university faculties, the hospitals, research institutes, and the Cancer Society. Special registries operate for oral precancerous conditions and for nasopharyngeal carcinoma (NPC). The topics of recent epidemiological studies include: a review of all cancers diagnosed at the University Hospital during 1972-74, the association of Epstein-Barr virus and NPC, social and environmental factors associated with NPC, oral cancers, and childhood cancers.
We conducted 2 case-control studies with Malaysian and Hong Kong Chinese and investigated the association between salted fish intake and nasopharyngeal carcinoma (NPC). Both studies show a highly significant association between salted fish intake, especially during childhood, and NPC. Furthermore, from our results we estimate that the majority of NPC cases occurring in the southern Chinese can be attributed to their consumption of this food early in life.
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.
No population-based cancer registry exists in Malaysia; thus our main sources of incidence data were biopsy series. We determined the frequency of cancers by body site, sex, and ethnic group from biopsy records of the Division of Pathology of the Institute for Medical Research in Kuala Lumpur for the years 1969-71. We then made comparisons of leading sites with data from the Singapore Cancer Registry. Relative risk values for 21 sites indicated significant differences among ethnic groups for cancers of the nasopharynx, larynx, lung, bone, skin, cervix, ovary, prostate, and penis and for lymphomas.