Importance of genetic testing for patients with multiple colorectal cancer primaries.

528Background: Individuals with hereditary colorectal cancer (CRC) may be at increased risk for a second primary CRC. Therefore, a personal history of multiple CRCs may be considered an indication for genetic testing. Methods: Multi-gene panel test (MGPT) results and age at CRC diagnoses were reviewed for 7046 CRC patients who underwent testing from March 2012 to June 2016. Depending on the panel ordered, analysis of up to 49 genes associated with CRC and/or other cancers was performed. The diagnostic yield and age at CRC diagnoses were compared between patients with a history of one CRC (n=6739) and those with two or more CRCs (n=307). Results: Individuals with a history of multiple CRCs had an overall positive rate of 23.8% (n=73), as compared to 12.4% (n=836) in those with a history of one CRC (OR=2.2; p=1.1E-7; 95%CI [1.653,2.907]). In the multiple CRCs group, 77 mutations were identified as follows: MLH1 (n=29), MSH2 (n=18), MSH6 (n=5), PMS2 (n=5), biallelic MUTYH (n=5), CHEK2 (n=5), APC (n=2), BRCA2...