Joint effects of family history and adult life dietary risk factors on colorectal cancer risk

Background. We analyzed the joint effects of family history of colorectal cancer and adult life dietary risk factors on colorectal cancer risk. Methods. We used data from a case-control study conducted in northern Italy between 1985 and 1992, including 1584 cases with colorectal cancer and 2879 controls. We created an adult life dietary risk factor score. Results. Among subjects with family history of colorectal cancer, those in the lowest risk score tertile were not at elevated risk of colorectal cancer (odds ratio = 1.2; 95% confidence interval = 0.7-2.1), whereas those in the highest score tertile were at increased risk (odds ratio = 5.5; 95% confidence interval = 3.5-8.7). Conclusions. These findings indicate that the expression of familial susceptibility can be substantially modified by adult life risk factors.