Dietary Factors in the Etiology of Cancer in Shanghai

Jian-Min Yuan, M.D., M.P.H., Ph.D.
University of Minnesota
Funded since 1987

This grant continues support for a residential cohort of 18,244 men in Shanghai, China, assembled during 1986-1989 when the men were between ages 45 and 64 years. At recruitment, all cohort members provided detailed dietary and medical histories, as well as blood and urine specimens. The cohort has been followed for the occurrence of cancer and death through routine ascertainment of new cases from the population-based Shanghai Cancer Registry and Shanghai Vital Statistics Units, and annual visits to all known surviving cohort members.

To date, the cohort has accumulated 204,010 person-years of observation. Only 231 study participants have been lost to follow-up. There have been 1,463 incident cancer cases, and 2,599 cohort members have died. The leading cancer sites are lung, liver, stomach, and colorectum. Stroke accounts for 23% of all deaths.

Active follow-up of this cohort continues. During the annual personal visit to each surviving cohort member, buccal cells are being collected to facilitate future etiologic studies involving DNA analysis. Although the investigators have been successful in harvesting DNA from serum samples collected at baseline, cost-based analysis revealed that it is more cost-effective for future gene-based studies to rely on this new source of DNA. Buccal cells are being collected from about 11,000 cohort members.

A series of nested case-control studies are being conducted to further elucidate the interplay of genetic and dietary factors in influencing cancer risk. Investigators are assessing the roles of:

• dietary aflatoxin and antioxidants (selenium, retinol, carotenoids, tea polyphenols) in cancers of the lung and liver;
• dietary isothiocyanates in cancers of the stomach, esophagus, and colorectum; and
• tea polyphenols in cancers of the stomach and esophagus.

In all instances of diet-cancer investigations, relevant genes with potential modifying effects on the respective diet-cancer associations will be included in the research.