Prevalence and family history of colorectal cancer: implications for screening

Objectives-To estimate the current prevalence of family history and associated risk of prevalent colorectal cancer among middle aged and older British adults. Methods-Cross sectional analysis of colorectal cancer and self reported family history based on data from a large population based study in Norfolk, United 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 colorectal cancer, 14.6% reported a family history of the disease. Also, a family history of colorectal cancer in first degree relatives was significantly associated 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 those 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 increased likelihood of colorectal cancer, screening strategies targeted solely at people with a family history will have Limited impact on reducing mortality from colorectal cancer at the population level.