Background: PPrefs of 467 US-based medical oncologists (MOs) in post-DO mCRPC pts were studied prospectively. A validated, proprietary, live, case-based market research tool was utilized with a core case scenario and 4 distinct treatment (Rx) outcomes following chemotherapy (CTx). Data were acquired using blinded audience response technology. Research support sources were double blinded. Methods: Core case: 59 y/o status post (s/p) radical prostatectomy with PSA failure after 15 months (mo), s/p salvage pelvic radiation (RT) → presents with rise in PSA and 3.5cm pelvic lymph node 16mo following RT→ progresses through multiple Rx over the next 42mo, including combined androgen blockade, anti-androgen withdrawal, sipuleucel-T and abiraterone (ABI). Now starting DO CTx due to increasing bone metastases and bone pain (BP). PPrefs for 4 variant scenarios of DO CTx were probed: (1) DO 75 mg/m²Q3wk x 6 cycles (cy) →Resolution of BP/PSA response → DO held due to cumulative myelosuppression/fatigue. Pt more active off CTx, ECOG PS 1. 3mo later →asymptomatic 30% rise in PSA. (2) DO x 4 cy → decrease in PSA, BP, node size. Prior to cy 6, has asymptomatic PSA progression. (3) DO x 4 cy→ decrease in PSA, BP, node size. Prior to cy 6, has both PSA and BP progression. (4) DO x 2 cy → progression with increased BP, PSA, and pelvic nodal disease. Results: See Table. Conclusions: PPrefs after DO CTx were outcome-dependent. In the absence of BP, ENZ is the most common PPref, even in this ABI-refractory pt. PPref for R223 over 2nd line CTx in the acquired symptomatic resistance setting is notable. PPref for 2nd line CTx increases with rapid, symptomatic disease progression.

Abbreviations: N/O, not offered.