Family cancer history affecting risk of colorectal cancer in a prospective cohort of Chinese women.

An elevated risk of colorectal cancer has been associated with sporadic colorectal cancer in first-degree relatives, mostly in Western populations. Limited data exist from traditionally low-risk areas, such as Asia, where the prevalence of risk factors may differ. We examined the association of family history of cancer and subsequent colorectal cancer risk in a cohort of traditionally low-risk Chinese women. We followed 73,358 women in the Shanghai Women's Health Study for cancer incidence until December 2005. After an average of 7 years of follow-up, 391 women were diagnosed with colorectal cancer. We calculated hazard ratios and 95% confidence intervals using Cox proportional hazards models adjusted for age, smoking, family income, education, body mass index, physical activity, and history of diabetes. We observed a significant association between colorectal cancer risk and history of a parent being diagnosed with colorectal cancer (hazard ratio: 3.34; 95% confidence interval: 1.58, 7.06). No association was observed for colorectal cancer diagnosed among siblings. Colorectal cancer risk was not influenced by a positive family history of cancer generally or any of the other cancers investigated (lung, breast, prostate, gastric, esophageal, endometrial, ovarian, urinary tract, central nervous system, and small bowel). Our cohort results suggest that consistent with findings from Western populations, having a family history of colorectal cancer may influence colorectal cancer risk to a similar extent in a low-risk population.