Singapore Cohort Study of Diet and Cancer

Mimi Yu, Ph.D.
University of Southern California/Norris Comprehensive Cancer Center
Department of Preventive Medicine
Los Angeles, Calif.
Funded since 1993

The current research project continues support for a residential cohort of 63,257 middle-aged and older (45 to 74 years) Singapore Chinese men and women accrued between 1993 and 1998. At recruitment, each study subject was interviewed in person by a trained interviewer using a structured questionnaire that emphasized current diet assessed via a validated, 165-item food frequency questionnaire.

Beginning in April 1994, a random 3% sample of cohort participants were asked to provide blood or buccal cell, and spot urine samples. This biospecimen collection was extended to all surviving cohort participants starting in January 2000. As of July 2003, biospecimens had been collected from close to 24,000 subjects, and the investigators expect to reach the target size of 30,000 by June 2004. They also asked for blood/buccal/urine specimens from all incident cases of female breast and colorectal cancers beginning in April 1994. This latter component will close when biospecimens have been collected from all consenting subjects.

The cohort has been passively followed for death and cancer occurrence through regular record linkage with the population-based Singapore Cancer Registry and the Singapore Registry of Births and Deaths. The observed numbers of incident cancers and deaths within the cohort are comparable to corresponding expected numbers based on age-sex-specific incidence rates for all Chinese in Singapore.

Significant scientific contributions of this prospective database include first reports of:

• an inverse association between soy intake and markers of breast cancer risk, including mammographic parenchymal patterns (Jakes et al., Cancer Epidemiology Biomarkers Prevention, 2002) and serum estrogens (Wu et al., Cancer Epidemiology Biomarkers Prevention, 2002).
• an adverse effect of soy intake on bladder cancer risk (Sun et al., Cancer Epidemiology Biomarkers Prevention, 2002).
• a protective effect of dietary isothiocyanates on colon cancer risk, especially among individuals deficient in glutathione S-transferases (Seow et al., Carcinogenesis, 2002).
• an adverse effect of n-6 fatty acids in the presence of low fish (or n-3 marine fatty acids) intake on breast cancer risk (Gago-Dominguez et al., British Journal of Cancer, 2003).
• application of statistical modeling to simultaneously correct for dietary measurement errors and residual confounding by smoking to demonstrate an unequivocal beneficial effect of dietary beta-cryptoxanthin on lung cancer risk (Yuan et al., Cancer Epidemiology Biomarkers Prevention, 2003).
• an association between angiotensin-converting enzyme genotype and breast cancer risk (Koh et al., Cancer Research, 2003).
• an association between vitamin D receptor genotype and colon cancer risk (Wong et al., Carcinogenesis, 2003).