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.