Risk of colorectal cancer for carriers of mutations in MUTYH, with and without a family history of cancer

We studied 2332 individuals with monoallelic mutations in MUTYH among 9504 relatives of 264 colorectal cancer (CRC) cases with a MUTYH mutation. We estimated CRC risks through 70 years of age of 7.2% for male carriers of monoallelic mutations (95% confidence interval [CI], 4.6%–11.3%) and 5.6% for female carriers of monoallelic mutations (95% CI, 3.6%–8.8%), irrespective of family history. For monoallelic MUTYH mutation carriers with a first-degree relative with CRC diagnosed by 50 years of age who does not have the MUTYH mutation, risks of CRC were 12.5% for men (95% CI, 8.6%–17.7%) and 10% for women (95% CI, 6.7%–14.4%). Risks of CRC for carriers of monoallelic mutations in MUTYH with a first-degree relative with CRC are sufficiently high to warrant more intensive screening than for the general population.