Duration of Short-Course Androgen Suppression Therapy and the Risk of Death As a Result of Prostate Cancer

We evaluated whether the duration of androgen suppression therapy (AST) had an impact on the risk of prostate cancer-specific mortality (PCSM) in men with unfavorable-risk prostate cancer (PC) within established Gleason score (GS) categories. Between February 2, 1996, and December 27, 2001, 761 men with unfavorable-risk PC were treated in Australia, New Zealand, Ireland, or the United States in a randomized trial with radiotherapy and 3, 4, or 6 months of AST (the study cohort). Competing risks regression was used to evaluate whether the duration of AST interacted with GS and was significantly associated with the risk of PCSM, adjusting for age, trial site, and PC prognostic factors. After a median follow-up of 10.9 years, 263 men died, 111 (42%) from PC. For all men, 6 versus 3 or 4 months of AST was associated with a reduced risk of PCSM (adjusted hazard ratio [AHR], 0.55; 95% CI, 0.36 to 0.82; P = .004). AHRs evaluating the impact of the duration of AST on the risk of PCSM were 0.67 (95% CI, 0.29 to 1.56; P = .35), 0.47 (95% CI, 0.25 to 0.85; P = .01), and 0.59 (95% CI, 0.30 to 1.19; P = .14) for men with GS ≤ 6, 7, and 8 to 10 PC, respectively. Therefore, the strongest evidence for this benefit was in men with GS 7 PC. AST durations of no less than 6 months should be considered when treating GS 7 PC with conventional dose RT.