Feasibility of tumor testing for BRCA status in high-grade serous ovarian cancer using fresh-frozen tissue based approach

Objective: For many years, BRCA mutational status has only been considered as a predictor of ovarian cancer susceptibility and as a prognostic factor. Nonetheless, in the era of precision medicine, it has also become a predictive biomarker of response to platinum-based-chemotherapy and, more recently, to PARP-inhibitors, also in the frontline setting. We assessed the feasibility of a fresh frozen tissue-based-BRCA-screening workflow in a tertiary referral center. Methods: We consecutively enrolled a series of 456 newly diagnosed FIGO-Stage IIIC-IV, high grade serous-ovarian cancer patients. All patients receiving tumor-biopsy underwent tBRCA-testing. Results: Clinically relevant tissue-BRCA (tBRCA) variants were observed in 145 women (31.8%), particularly we recognized 89 (61.4%) patients with BRCA1-pathogenetic variants (PVs) and 56 women (38.6%) with BRCA2-PVs. Among 292 tBRCA wild-type (wt) patients, 88 cases were germline BRCA tested (gBRCA) and 86 (97.8%) were confirmed as gBRCAwt, while 1 (1.1%) had gBRCA variant of uncertain significance and 1 had gBRCA mutation (1.1%). The concordance of tumor test versus germline BRCA test was 86.3% (209/242). Large genomic rearrangements (LGRs) were suspected in 13/292 tBRCAwt patients (4.5%) by using bioinformatic algorithm and multiplex ligation-dependent probe amplification (MLPA) was performed, with evidence of PVs in only 1 case. Conclusions: Fresh-frozen tissue-based BRCA screening workflow is feasible and reliable. It allows to enlarge the BRCA mutated population that might receive PARPi with the greatest benefit, without missing cascade testing for family members and therefore, maintaining its preventive role.