Patterns of gastro-intestinal cancer in European migrants to Australia: the role of dietary change.

Cancers of the stomach, pancreas, colon and rectum are increasingly regarded as being diet-influenced. Migrants to Australia from England, Scotland, Ireland, Poland, Yugoslavia, Greece, and Italy have come from countries with varied dietary backgrounds and gastrointestinal cancer risks. Age-standardized cancer death rates in migrrants, by country of origin, sex, age, and duration of residence in Australia (less than or equal to 16 years and greater than 16 years), have been calculated for 1962-76, and compared with those of the Australian-born population. All seven migrant source countries, in 1970, had higher rates of stomach cancer than Australia, and the corresponding migrants groups, which initially reflected those higher rates, experienced an approximately 25% risk reduction with increased duration of residence. For cancer of the pancreas, migrants initially had rates well above their "native" rates; with longer stay, the risks generally converged upon that of the Australian-born population. The four "continental" (European) migrant groups, whose native risk of colon cancer is about half that of the Australian population, showed an increased risk with increasing duration of stay. The increase was greater in men than in women, perhaps reflecting their greater dietary acculturation. By contrast, Scottish migrants, with an initially high risk of cigrants showed even larger increases than colon cancer, while in British migrants there was a marked decline towards the "Australian-borne" risk. These various changes in cancer risk are discussed with reference to inter-country dietary differences.