Incidence of colorectal cancer in BRCA1 and BRCA2 mutation carriers: results from a follow-up study.

The BRCA1 and BRCA2 genes confer increased susceptibility to breast and ovarian cancers (Wooster et al, 1995; Ford et al, 1998; Satagopan et al, 2001; Thompson et al, 2001; Antoniou et al, 2003) and to a spectrum of other cancers (Struewing et al, 1997; Breast Cancer Linkage Consortium, 1999; Brose et al, 2002; Thompson and Easton, 2002; King et al, 2003). However, the risk for colorectal cancers associated with BRCA1 and BRCA2 mutations remains unclear. Previous studies that were designed to estimate the risk of colon cancer among mutation carriers were based on cross-sectional reviews of family histories of women with mutations and were susceptible to both selection bias and misclassification. The diagnoses of colorectal cancer were based on information provided by a family member and this approach may not always be accurate. Further, in previous studies, the mutation status of the colorectal cancer cases was unknown. We conducted a prospective study of the incidence of colorectal cancer in a cohort of BRCA1 and BRCA2 mutation carriers. We followed 7105 women with a BRCA1 or a BRCA2 mutation for a mean of 5.5 years. The knowledge of colorectal cancer incidence rates has important implications for genetic counsellors and their patients and for developing appropriate screening policies.