Shilpa Grover, M.D., M.P.H., from Brigham and Women's Hospital in Boston, and colleagues examined the prevalence of pathogenic APC and MUTYH mutations in 8,676 patients with multiple colorectal adenomas. Participants had undergone full gene sequencing and large rearrangement analysis of the APC gene, with targeted sequence analysis for the two most common MUTYH mutations (Y179C and G396D). Full MUTYH gene sequencing was conducted in individuals with either mutation.

The researchers found that 7,225 individuals had colorectal adenomas (1,457 patients had classic polyposis with ≥100 adenomas and 3,253 had attenuated polyposis with 20 to 99 adenomas). The prevalence of pathogenic APC and bilallelic MUTYH mutations was 80 and 2 percent, respectively, for those with 1,000 or more adenomas; 56 and 7 percent, respectively, for those with 100 to 999 adenomas; 10 and 7 percent, respectively, for those with 20 to 99 adenomas; and 5 and 4 percent, respectively, for those with 10 to 19 adenomas. In multivariable analyses, adenoma count correlated strongly with a pathogenic mutation.

"The mutation probabilities reported here may assist clinicians in their decision to recommend genetic evaluation and counsel patients undergoing genetic testing," the authors write.

Several authors disclosed financial ties to diagnostic and health care companies, including Myriad Genetic Laboratories, which forwarded data sets to the independent investigators.

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