Family history and risk of colorectal cancer: implications for screening programmes

Objective To estimate the lifetime risk of colorectal cancer in the general population and in first degree relatives of patients with sporadic colorectal cancer or adenoma. Main outcomes measures The cumulative risk of colorectal cancer (0–74) in the general population combined with the relative risk of colorectal cancer and the prevalence of different groups of subjects with family history of colorectal tumour allows the calculation of cumulative risks in these groups. Results The lifetime risk of colorectal cancer was 1 in 23 in men and 1 in 40 in women. In males, 0.5% in the 55–59 age group and 4.5% in the 70–74 age group will develop a colorectal cancer. The corresponding values in females were 0.4% and 2.5%. The cumulative risk at age 74 varied between 7.7% (one family member affected) and 25.6% (two affected) in males, and 4.3% and 14.3% respectively in females. The risk in the 40–44 year age group for individuals with one first degree relative affected before 45 years of age was 0.5%, similar to that of those aged 45–49 with one first degree relative affected with a colorectal cancer or a large adenoma (> 1 cm). Conclusions These results suggest that screening in the general population should start at 50 or 55. The lifetime risk is high enough (over 10%) among individuals with one affected first degree relative before age 45, or with at least two affected first degree relatives, to warrant colonoscopic screening. The data provide a basis for recommendations that relatives of these patients should enter screening programmes at age 40 to 44.