Introduction: Approximately 10-15% of unselected prostate cancer (PCa) patients (pts) have a pathogenic germline variant (PGV). Identification of a PGV can inform cancer screening, treatment selection, and family cascade testing. Limited data are available on clinician recommendations following germline genetic testing (GGT) in PCa pts. This study collected clinician-reported changes to PCa care (treatment, follow up and cascade testing) based on GGT results. Methods: An IRB-approved, nationwide, prospective registry recruited unselected, newly (within 12 months of enrollment) or previously diagnosed (>12 months prior to enrollment), PCa pts from 15 community and academic urology practices. Pts underwent an 84-gene panel test and results were grouped as positive (=1 PGV), VUS (variant(s) of uncertain significance)-only, or negative. Clinician recommendations were collected via electronic case report forms >1-month post GGT. Statistical significance was determined by two-tailed Fisher’s exact test and significance was set at p<0.05. Results: 982 predominantly white (76%), non-metastatic (81%) males with PCa were recruited; 50% met 2019 PCa National Comprehensive Cancer Network (NCCN) GGT criteria. 102 PGVs in 24 cancer risk genes, most commonly CHEK2 and BRCA2 (17 and 10 pts, respectively) were identified in 100 (10%) pts, 50% of whom did not meet GGT criteria. Positive pts were more likely to have changes to treatment, follow up and cascade testing than those with negative or VUS-only results (Table 1). Among positive pts, there were no significant differences in recommendations for pts who met NCCN criteria versus those who did not (Table 1). However, more treatment changes were made for metastatic pts than non-metastatic pts and for those with high-grade (Gleason grade 4/5) compared to medium-to-low-grade disease (Gleason grade <4) (Table 2). Conclusions: This study showed that GGT did influence PCa pt care and lends support to universal testing of PCa pts. SOURCE OF Funding: Research Grant from Invitae
