Identifying patients that may benefit from addition of bicalutamide to salvage radiation therapy in the setting of biochemical failure after radical prostatectomy

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Conference Proceeding

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European Urology Open Science


Introduction & Objectives: It is generally agreed that salvage radiation therapy (sRT) improves outcomes in patients that experience biochemical failure after radical prostatectomy. Adding anti-androgen therapy (AAT) improves outcomes further, but not in all. This study aimed to elucidate which patients derive benefit from a combination of AAT and sRT.

Materials & Methods: Data on 760 men who participated in the RTOG 9601 trial were extracted using the NCTN data archive platform. Patients were stratified into 2 groups, those that received sRT alone and those that received both sRT and bicalutamide. To analyze the impact bicalutamide versus no AAT on 10-yrs overall survival, interaction between 10-yrs predicted mortality probability and AAT/no AAT was plotted using locally-weighted methods controlling for all baseline factors; a two sided p<0.05 was considered significant.

Results: The lines for bicalutamide and no AAT separated at 10-yrs predicted mortality risk of 10%, indicating that patients with a predicted 10-yrs mortality risk of 10% or greater will benefit from bicalutamide (Figure). Cox-regression analysis demonstrated that patients undergoing combination bicalutamide and sRT (HR=1.34, 95% CI 1.18-1.52) had 16% lower hazard of mortality as compared to patients undergoing sRT alone (HR=1.51, 95% CI 1.36-1.67) for every 10% increment in predicted mortality risk (p<0.001).

Conclusions: In patients with biochemical failure after RP, only patients with mortality risk of 10% or greater benefit from the addition of AAT to sRT. Combining bicalutamide and sRT shows a 16% added survival benefit for every 10% incremental increase in 10-yrs mortality risk.



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