Continued Benefit to Androgen Deprivation Therapy for Prostate Cancer Patients Treated With Dose-Escalated Radiation Therapy Across Multiple Definitions of High-Risk Disease

Purpose: To analyze prognostic factors in patients with high-risk prostate cancer treated with dose-escalated external-beam radiation therapy (EBRT) and androgen deprivation (ADT). Methods and Materials: Between 1998 and 2008 at University of Michigan Medical Center, 718 men were consecutively treated with EBRT to at least 75 Gy. Seven definitions of high-risk prostate cancer, applying to 11–33% of patients, were evaluated. Biochemical failure (BF), salvage ADT use, metastatic progression, and prostate cancer–specific mortality (PCSM) were estimated by the Kaplan-Meier method and Cox proportional hazards regression. Results: Each high-risk definition was associated with increased BF (hazard ratio [HR] 2.8–3.9, p < 0.0001), salvage ADT use (HR 3.9–6.3, p < 0.0001), metastasis (HR 3.7–6.6, p < 0.0001), and PCSM (HR 3.7–16.2, p < 0.0001). Furthermore, an increasing number of high-risk features predicted worse outcome. Adjuvant ADT yielded significant reductions in both metastases (HR 0.19–0.38, p < 0.001) and PCSM (HR 0.38–0.50, p < 0.05) for all high-risk definitions (with the exception of clinical Stage T3–4 disease) but improved BF only for those with elevated Gleason scores (p < 0.03, HR 0.25–0.48). When treated with ADT and dose-escalated EBRT, patients with Gleason scores 8 to 10, without other high-risk features, had 8-year freedom from BF of 74%, freedom from distant metastases of 93%, and cause-specific survival of 92%, with salvage ADT used in 16% of patients. Conclusion: Adjuvant ADT results in a significant improvement in clinical progression and PCSM across multiple definitions of high-risk disease even with dose-escalated EBRT. There is a subset of patients, characterized by multiple high-risk features or the presence of Gleason Pattern 5, who remain at significant risk for metastasis and PCSM despite current treatment.