MP79-09: ANTI-ANDROGEN THERAPY OVERCOMES THE TIME-DELAY IN INITIATION OF SALVAGE RADIATION THERAPY AND RESCUES ONCOLOGICAL OUTCOMES IN MEN WITH RECURRENT PROSTATE CANCER AFTER RADICAL PROSTATECTOMY

Akshay Sood, Jacob Keeley, Deepansh Dalela, Sohrab Arora, Isaac Palma-Zamora, Marcus Jamil, Natalija Kovacevic, Guillaume Farah, Philip Olson, Wooju Jeong, Quoc-Dien Trinh, Craig G. Rogers, James O. Peabody, Mani Menon, Firas Abdollah

Introduction: To examine whether the addition of anti-androgen therapy (AAT) to ‘late’ salvage radiation therapy (sRT) can lead to oncological outcomes similar to that of early sRT in men with recurrent prostate cancer after radical prostatectomy.

Methods: Data on 670 men who participated in the RTOG 9601 trial and experienced biochemical recurrence were extracted using the NCTN data archive platform. Patients were stratified into four treatment groups: early sRT (pre-sRT PSA <0.7 ng/mL) with/without concomitant AAT and late sRT (pre-sRT PSA ³0.7 ng/mL) with/without concomitant AAT, based on the cut-offs reported in the original trial. Cox proportional hazards and Fine-Gray competing-risk regression analyses assessed the adjusted hazards of overall mortality, CaP specific mortality and metastatic/local disease progression among the four treatment groups.

Results: Patients were well-matched in baseline characteristics. The median follow-up was 12 years. At 10-years, for patients treated with early sRT, early sRT with AAT, late sRT and late sRT with AAT, the overall mortality, CaP specific mortality and metastasis rates were 14%, 16%, 31% and 17% (Log-rank p=0.0001), 7%, 3%, 16% and 4% (Gray’s p=0.0001) and 12%, 9%, 26% and 12% (Gray’s p=0.0003), respectively (Figure). Adjusted analysis demonstrated increased hazards of overall mortality in patients receiving delayed sRT versus early sRT, HR 1.62 (95% CI: 1.11 - 2.37). However, no difference remained after addition of concomitant AAT to late sRT ¾ referent early sRT, HR 0.89 (95% CI: 0.58 - 1.39). Similarly, the hazards of cancer-specific mortality and metastatic progression were worse for late sRT, when compared to early sRT, but were no different after addition of AAT to late sRT.

Conclusions: Poorer outcomes associated with late sRT may be rescued with delivery of concomitant AAT. Source of

Funding: None