Prevalence and family history of colorectal cancer: implications for screening

Objectives-To estimate the current prevalence of family history and associa ted risk of prevalent colorectal cancer among middle aged and older British adults. Methods-Cross sectional analysis of colorectal cancer and self reported fam ily history based on data from a large population based study in Norfolk, U nited Kingdom. Results-Of the 30 353 participants, 2069 (6.8%) participants had reported a family history of colorectal cancer in at least one first degree relative. The prevalence of colorectal cancer in those with a family history was 1% and 0.5% in those without. Of the 151 participants with prevalent colorecta l cancer, 14.6% reported a family history of the disease. Also, a family hi story of colorectal cancer in first degree relatives was significantly asso ciated with an increased risk of prevalent colorectal cancer (multivariate odds ratio (OR) 2.32 (95% confidence interval (95% CI) 1.43 to 3.76). For t hose with one affected relative below the age of 45, and for those with two affected relatives the multivariate ORs were 5.29 (1.63 to 17.17) and 4.93 (1.17 to 20.70), respectively. Conclusions-Although positive family history may identify a group with incr eased likelihood of colorectal cancer, screening strategies targeted solely at people with a family history will have Limited impact on reducing morta lity from colorectal cancer at the population level.