Background: Colorectal cancer screening through colonoscopy has long been recognized as the gold standard in detecting precancerous lesions. Approximately 40% to 50% of asymptomatic individuals undergoing screening colonoscopy will have at least 1 polyp removed, and 20% of individuals have multiple polyps removed. Genetic testing for polyposis was initially evaluated in high-risk families. Therefore, prior to January 2015, the National Comprehensive Cancer Network (NCCN) guidelines recommended any individual with > 10 lifetime adenomas be referred for genetic counseling and possible genetic testing. Revised guidelines increased the suggested number of adenomas required for testing from 10 to 20.The NCCN guidelines stipulate ordering of APC and/or MUTYH gene testing at the discretion of the clinician. Assessment prior to testing should include eliciting a family history and other lifestyle factors. Several risk factors associated with increased polyp burden include age, gender, smoking, body mass index, and diet. In addition, there is little guidance for situations in which genetic testing is unlikely to be informative or change management. Despite this, there are few data to suggest testing may have low utility for individuals with multiple risk factors that are the more likely cause of polyposis. Considering many veterans are smokers and have other risk factors, the VHA is in a unique position to assess the utility of genetic testing for inherited polyposis in a general population screening setting.
Purpose: To describe the characteristics of veterans with more than 10 adenomas who were tested for APC and MUTYH mutations and determine the frequency of mutations.
Methods: Retrospective chart review of individuals who had counseling and genetic testing for APC/MUTYH through the Genomic Medicine Service. Veterans were excluded if they presented for reasons other than routine colon screening or surveillance.
Results: Five out of 81 (6%) veterans who met inclusion criteria had a pathogenic mutation in APC or 2 pathogenic mutations in MUTYH. Only 1 of those individuals had fewer than 20 adenomas prior to testing.
Conclusions: Our results support the recent revisions to NCCN testing guidelines. Our experience suggests the need for integration of other factors into risk assessment beyond total number of adenomas detected, including known risk factors and age at first colonoscopy.
