Pilot Study Of Clinical Targeted Next Generation Sequencing For Prostate Cancer: Consequences For Treatment And Genetic Counseling.

251 Background: Targeted next generation sequencing (NGS) panels for identification of actionable mutations are increasingly used in oncology for therapeutic decision-making, but have yet to be widely used for prostate cancer.To determine the utility of applying a targeted next generation sequencing to prostate cancer management, we conducted a pilot study using the clinical molecular diagnostic assay, UW-OncoPlex, on primary and metastatic tumors from patients with prostate cancer. Methods: Patients receiving treatment for prostate cancer by a medical oncologist were eligible. After providing informed consent, tumor DNA was extracted from formalin-fixed, paraffin-embedded (FFPE)primary tumors and/or metastatic biopsies. Extracted DNA was analyzed using UW-OncoPlex, a targeted NGS panel designed to assess genomic alterations in 234 cancer-associated genes (PMID: 24189654). Results were discussed at a monthly multidisciplinary precision tumor board prior to communicating results to patients. Results: Forty patients consented to the study and 31 (78%) had reportable results. Findings included frequently observed prostate cancer genomic aberrations, including: TMPRSS2-ERG fusions and copy-number alterations of PTEN, TP53, FOXA1, AR, and SPOP. We also observed potentially actionable alterations in BRAF, MAP2K1 (MEK1), PIK3R1, MET, FGFR1, and FGFR3, which inform future treatment and clinical trial considerations. Notably, 8/31 (25%) patients had suspected high penetrance germline mutations, including in BRCA2 (N = 3), TP53 (N = 2), ATM (N = 1), and CHEK2 (N = 2). These 8 individuals were referred to medical genetics and 7 of 8 mutations were confirmed to be germline. One patient was found to have a hypermutated phenotype associated with bi-allelic MSH6 mutation and microsatellite instability. Conclusions: Targeted NGS panel testing may be useful in informing future treatment approaches and clinical trial selection for patients with prostate cancer. In addition, we observed a high proportion of cases with suspected high-penetrance germline mutations and immediate actionability through referral to medical genetics.