Circulating tumor (ct)-DNA alterations in metastatic castration-resistant prostate cancer (mCRPC): Association with outcomes and evolution with therapy.

149Background: Cell-free ctDNA may be prognostic and evolve following therapy. We report ctDNA profiling of patients (pts) with mCRPC and their association with clinical outcomes and evolution with therapy. Methods: Pts with mCRPC that underwent baseline ctDNA analysis for potentially actionable alterations using Guardant360 before new systemic therapy were identified. Data were requested for clinical factors, current and prior therapy, TTF (time to failure) and survival. A 70-gene cfDNA next generation sequencing panel from a CLIA-licensed, CAP-accredited laboratory (Guardant Health, Inc.) offers complete exon sequencing for 29 genes, critical exons in 39 genes and amplifications (16 genes), fusions (6 genes) and indels (3 genes) harvested from 10 mL of peripheral blood. Alterations were reported and association of alterations with outcomes and prior therapy was examined. Results: Of 514 with confirmed mCRPC, 482 (94%) had ≥ 1 ctDNA alteration. The median age was 70 years (range 39-91). The most common r...