176 Background: Independently, dose-escalated external beam radiation therapy (DE-EBRT) and short-term androgen deprivation therapy (ADT) improve outcomes for men with intermediate-risk prostate cancer; however, the incremental benefit of adding short-term ADT to DE-EBRT is uncertain. The aim of this study was to determine the effect of adding ADT to DE-EBRT and to identify men most likely to benefit from ADT. Methods: We reviewed the medical records of 636 men treated for intermediate-risk prostate cancer with DE-EBRT (>75 Gy) from 1995 to 2009. The adult comorbidity evaluation-27 index categorized severity of comorbidity. Recursive partitioning analysis defined unfavorable disease. Kaplan-Meier and log-rank tests compared failure-free survival (FFS) with and without ADT. Results: Median age was 70 years (interquartile range [IQR] 65–74). Overall, 45% received DE-EBRT alone and 55% DE-EBRT with ADT (median 6 months, IQR 6-8). Median follow up was 4.3 years. On Cox-proportional hazard regression analysis that adjusted for differences in comorbidities and tumor characteristics, administration of ADT improved FFS (adjusted hazard ratio 0.36, 95% confidence interval 0.18–0.72; p=0.004). Recursive partitioning analysis of men without ADT classified Gleason 4+3=7 or ≥ 50% positive cores as unfavorable disease (5-year FFS 96.3% favorable vs. 81.6% unfavorable; p<0.001). The addition of ADT to DE-EBRT improved 5-year FFS for men with unfavorable disease (n=334; 81.6% vs. 92.9%; p=0.009) but did not improve FFS for men with favorable disease (n=302; 96.3% vs. 97.4%; p=0.874). When stratified by comorbidity, ADT improved FFS for men with unfavorable disease and no or mild comorbidity (p=0.006) but did not improve FFS for men with unfavorable disease and moderate to severe comorbidity (p=0.380). Conclusions: The addition of ADT to DE-EBRT improves FFS for men with unfavorable intermediate-risk prostate cancer (Gleason 4+3=7 or ≥ 50% positive cores) especially those with no or minimal comorbidity. Men with favorable intermediate-risk disease or with moderate to severe comorbidity may not benefit from the addition of ADT to DE-EBRT.
Surrogate End Points for All-Cause Mortality in Men With Localized Unfavorable-Risk Prostate Cancer Treated With Radiation Therapy vs Radiation Therapy Plus Androgen Deprivation Therapy
