Determining the clinical value of germline genetic testing coupled with tumor mutation profiling.

Abstract

1577 Background: Somatic mutation analysis by next-generation sequencing (NGS) is an expanding clinical assessment offered to cancer patients. Studies report that 4–12% of patients have a positive tumor mutation profiling (TMP) result in a known cancer predisposition gene also identified in their germline, which has potential implications for the patient’s acute treatment, ongoing surveillance, and the screening of family members. We report a series of patients with TMP coupled with germline genetic testing and include yield of pathogenic germline mutations, discordance between germline and TMP findings, and potential clinical impact. Methods: Our study used de-identified data from 182 consecutive patients who underwent TMP followed by germline testing with an NGS-based hereditary cancer gene panel. Results: 50/182 cases (27%) had one or more likely pathogenic or pathogenic (LP/P) germline variants, which is higher than previous reports. Among these 50, 28 (56%) met guidelines for germline testing by personal or family history criteria, 10 (20%) met recently established NCCN criteria for germline testing of patients with BRCA1/2 tumor variants, and 12 (24%) had TMP results that suggested a germline mutation but did not meet any guidelines for germline testing. We identified 52 LP/P germline variants in BRCA2 (17), BRCA1 (7), PALB2 (6), MUTYH (5), CHEK2 (2), and 15 other genes, all with established guidelines that would impact the clinical management of patients and their family members. In 9/50 cases, germline testing revealed variants that were absent in TMP results and provided new information with clinical implications for patients and their families, including variants in BRCA1 and CHEK2. Conclusions: In TMP patients, 50 of 182 had a medically actionable germline mutation with established management guidelines. Among these 50, 12 (24%) met neither current personal or family criteria nor the latest NCCN guidelines for germline testing in patients with TMP. Also striking were nine patients whose germline LP/P mutations were absent in TMP results. These data suggest that indications for germline testing of cancer patients must be expanded to avoid missing important germline findings in patients undergoing TMP.