Simultaneous germline and somatic sequencing in ovarian carcinoma: mutation rate and impact on clinical decision-making

Abstract Objective Germline and somatic BRCA1 and BRCA2 (BRCA) mutations predict treatment response in patients with epithelial ovarian, peritoneal or fallopian tube cancer (OC), yet only germline testing is routinely pursued or reimbursed at diagnosis. We report our experience with clinical testing of paired tumor and germline DNA for OC mutations. Methods Simultaneous sequencing using the BROCA assay of DNA from paired blood and neoplastic tissue became clinically available at our institution in 2017. We retrospectively reviewed the medical records of OC cases tested from 7/2017 to 7/2018. We calculated the rates of known pathogenic germline mutations and actionable somatic mutations, defined as those for which targeted therapies exist. Results We identified 43 women (36 new diagnoses, seven recurrences) who underwent testing. Average age at diagnosis was 60. OC samples came from surgical specimens in 31 cases (72.1%), from biopsy in 11 cases (25.6%), and from cytology in one case (2.3%). We identified pathogenic germline mutations in six cases (14%), actionable somatic mutations in 15 cases (35%), and both a somatic and germline mutation in one case (2%). BRCA mutations accounted for 59% of all mutations. Of 40 cases with sufficient follow-up, providers documented reviewing results of genetic testing in 34 (85%), which influenced clinical decisions in 12 (30%). Conclusions Simultaneous germline and tumor sequencing is an efficient way to provide enhanced information to guide the care of OC patients. This approach can identify somatic BRCA mutations at diagnosis, allowing physicians to provide PARP inhibitor maintenance and improve outcomes for those patients.