Prevalence of variant of unknown significance (VUS) in men with prostate cancer who serve as a benchmark for enhanced screening and for personalized therapy.

Abstract

342 Background: Pathogenic variants (PVs) in DNA repair genes (DRG), such as in BRCA1, BRCA2, ATM, CHEK2, etc., have implications for prostate cancer (PCa) family genetic counselling, testing and risk stratification in men. However, understanding how to counsel patients with variants of unknown significance (VUS) is an unmet clinical need. On the other hand, there is the necessity to cautiously interpret VUS findings and to bolster VUS evaluations with additional evidence for pathogenicity. In this study, we aim to investigate the prevalence of germline VUS in men with PCa and their association with outcomes after robot-assisted radical prostatectomy (RARP). Methods: This is a nested cohort case study from an ongoing PCa screening, set to identify and screen men in the Italian population with a genetic predisposition (AIRC - Fondazione AIRC per la Ricerca sul Cancro project IG 2020 ID 25027). Cases for the current analysis were selected by “Adam's rib strategy” searching for germline DRG variant in men with a diagnosis of high-risk PCa who were scheduled for RARP. After informed consent was signed, a blood sample was obtained. A previously validated multigene panel test was used to assess the presence of germline variants. PVs and VUS were classified according to the American College of Medical Genetics and Genomics and Association for Molecular Pathology consensus criteria and International Agency for Research on Cancer guidelines. The primary endpoint was to describe the prevalence of VUS and the secondary to correlate VUS with pathological outcomes after RARP. Results: A total of 118 men with diagnosis of PCa who underwent RP were enrolled. The mean age at diagnosis of PCa was 65.9 (±6.42) years; pathological grade was ISUP 1-2 in 58.0% patients and 3-5 in 42.0%. Of the 76 men evaluated, 18 (23.7%) had a VUS and 1 (1.32%) a pathogenic germline variant in BRCA1 and PALB2. Among those with VUS younger men at diagnosis were more likely to carry a VUS than older at diagnosis mean (age 64 ± 6.41 vs. 66 ± 7.20 years). Additionally, 33.3% vs 16.2 % were carrier of VUS and N+ and required adjuvant androgen deprivation therapy. No difference between ISUP at final pathology and positive margin rate were found. Conclusions: Our findings showed a high prevalence of VUS germline mutations in PCa patients undergoing RARP. These mutations seem to be associated with worse pathological outcomes. Limitations includes short follow-up and absence of non-Caucasian patients.