CANCER MORTALITY AMONG CHINESE MIGRANTS - A REVIEW

Background. Epidemiological studies of cancer among migrant groups are beneficial in that they can provide insight into genetic and environm ental factors in disease aetiology. Seven studies in the epidemiologic al literature have examined cancer mortality in migrants from China; m ethodological features and findings, which display remarkable consiste ncies between studies, are reviewed here. Methods. Papers were include d that compare site-specific cancer mortality patterns in first and se cond generation migrants to the experience in the host regions using v ital statistics and census data. Rates had to be standardized either i ndirectly (using age-specific rates from the host regions) or directly (using a standard age structure) and standardized mortality ratios (S MR) or rate ratios (RR) were calculated. Results. Migrant males had ov erall mortality from cancer that was often in significant excess compa red to the host experience; results for females (for overall cancer) w ere equivocal. Both sexes had large and significant excess mortality f rom nasopharyngeal and liver cancer; SMR and RR were also consistently elevated for cancers of the stomach and oesophagus. There was notable attenuation in the high risk at these four sites in the second genera tion. All studies reported pronounced and significant reduced risk for prostatic cancer and female breast cancer, with little or no increase in mortality in the second generation. The SMR and RR also tended to be below unity for brain, bladder and kidney cancer. Conclusions. The results of this review indicate that cancer risk at several sites amon g Chinese migrants appears to be in transition, and that these finding s are consistent across studies.