Identifying patients that may benefit from addition of bicalutamide to salvage radiation therapy in the setting of biochemical failure after radical prostatectomy
Kovacevic N, Sood A, Keeley J, Dalela D, Arora S, Palma-Zamora I, Jamil M, Jeong W, Trinh QD, Rogers CG, Peabody JO, Menon M, and Abdollah F. Identifying patients that may benefit from addition of bicalutamide to salvage radiation therapy in the setting of biochemical failure after radical prostatectomy. European Urology Open Science 2020; 19:e1063.
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.