The Need for Androgen Deprivation Therapy in Patients With Intermediate-Risk Prostate Cancer Treated With Dose-Escalated External Beam Radiation Therapy

To evaluate if androgen deprivation therapy (ADT) improves outcomes for patients with localized, intermediate-risk prostate cancer treated with definitive external beam radiation therapy (EBRT) in the dose-escalated era. This is a retrospective study using a prospective database at a single institution. We included patients with localized, intermediate-risk prostate cancer (any of the 3 risk factors: PSA 10-20 ng/mL, Gleason 7, T2b-T2c) treated with dose-escalated RT with 3-dimensional conformal RT or intensity modulated RT (74-80 Gy in daily fractions of 1.8 Gy-2.0 Gy, or 70.2 Gy in daily fractions of 2.7 Gy) from 1992 to 2013. Patients with prior treatment for prostate cancer, those on long-term ADT (≥23 months), or those with follow-up <1 year were excluded. We defined initial ADT as initiation within 9 months prior to the start of RT, during RT, or within 2 months after the completion of RT. Outcomes for patients who received initial ADT were compared to men treated with RT alone. Covariates included number of intermediate risk factors, age, and baseline comorbidities. Kaplan Meier estimates were compared using log-rank tests. Competing risk regression and Cox proportional hazards regression were used to estimate hazard ratios adjusted for covariates. Of 1134 patients included in this study, 155 received initial ADT with median duration of 4.0 months (range 0.5-22.0 months). The median follow up was 56.4 months (range 12.3-200.7 months). Patients on ADT had more risk factors (RF) compared to those with RT alone (1 RF: 63.2% vs 73.4%, 2 RFs: 31.6% vs 23.8%, 3 RFs: 5.2% vs 2.8%, P=.021). When patients with ADT were compared to those treated with RT alone, there were no significant differences in freedom from biochemical failure (BCF) (84.0% vs 87.3%, P=.83), freedom from distant metastasis (DM) (94.4% vs 96.9%, P=.41), or overall survival (OS) (92.3% vs 90.7%, P=.48) at 5 years. When patients with ADT duration of 3 to 12 months (n=105) were compared to those treated with RT alone, there were still no significant differences in BCF, DM, or OS. In multivariable analyses adjusting for number of RFs and age, the adjusted hazard ratio for ADT use was sHR=1.02 (95% CI 0.63-1.63, P=.95) for BCF; sHR=1.28 (95% CI 0.56-2.93, P=.56) for DM. For overall mortality, adjusted HR= 1.25 (95% CI 0.77-2.05, P=.36) where comorbidities (including diabetes, cardiac disease, and hypertension) were also included as covariates. Treatment of intermediate-risk prostate cancer with definitive dose-escalated EBRT alone resulted in acceptable outcomes. Despite minor differences in patient selection, ADT (up to 22.0 months) was not associated with improved outcomes.