Monoallelic MUTYH pathogenic variants ascertained via multi-gene hereditary cancer panels are not associated with colorectal, endometrial, or breast cancer.

We aimed to determine whether monoallelic MUTYH pathogenic and likely pathogenic variants (PVs) are associated with colorectal, breast, and endometrial cancer. Cases were individuals with colorectal, female breast, or endometrial cancer who reported European ancestry alone and underwent a multi-gene hereditary cancer panel at a large reference laboratory. Controls were individuals of European (non-Finnish) descent from GnomAD with cancer cohorts removed. We performed a Fisher's exact test to generate odds ratios (ORs) with 95% confidence intervals (CI). Prevalence of single MUTYH PVs in cancer cohorts versus controls, respectively, was: colorectal cancer, 2.1% vs. 1.8% (OR 1.2, 95% CI 0.99-1.5, p = 0.064); breast cancer 1.9% vs. 1.7% (OR 1.1, 95% CI 0.96-1.3, p = 0.15); and endometrial cancer, 1.7% vs. 1.7% (OR 0.98; 95% CI 0.70-1.3, p = 0.94). Using the largest colorectal and endometrial cancer cohorts and one of the largest breast cancer cohorts from a single case-control study, we did not observe a significant difference in the prevalence of monoallelic MUTYH PVs in these cohorts compared to controls. Additionally, frequencies among cancer cohorts were consistent with the published MUTYH carrier frequency of 1-2%. These findings suggest there is no association between colorectal, endometrial, or breast cancer and MUTYH heterozygosity in individuals of European ancestry.