Impact of Race on Both Pathologic Extent of Disease and Administration of Adjuvant Radiation Therapy in a Cohort With Clinical Low-Risk Prostate Cancer Undergoing Radical Prostatectomy

Abstract

Purpose/Objective(s): Androgen deprivation therapy (ADT) and standard dose external beam radiation therapy ( 70 Gy) have improved biochemical outcomes in intermediate risk (IR) prostate cancer. It is not known whether ADT improves outcomes in patients treated with brachytherapy. Our purpose is to evaluate the impact of ADT on biochemical failure free survival (bFFS) and overall survival (OS) in a multi-institutional database of IR prostate cancer patients treated with low dose rate prostate brachytherapy (LDR BT). Materials/Methods: From the Genitourinary Radiation Oncologists of Canada (GUROC) Prostate Cancer Risk Stratification (ProCaRS) database, a cohort of 859 patients with IR prostate cancer treated with LDR BTwith or without ADT was identified. Propensity scores were generated using multivariate regression based on age, baseline PSA, Gleason score and clinical stage. Patients treated with LDR alone were each matched to 2 patients who received the combination of LDR and ADT. Results: A 1:2 matching scenario (175 LDR BT : 350 LDR BT+ADT) provided the best balance of adjusted prognostic factors, a larger sample size than obtained with 1:1 matching, and standardized differences< 0.1 for prognostic factors used for matching. The 2 groups were balanced for age, baseline PSA, Gleason score and clinical stage. Median follow-up was longer in the LDR BT+ADT group (7.15 vs 4.21 years). After matching, there was no difference in bFFS (relative risk LDRBT+ADTZ 0.87, 95%CIZ 0.50-1.53); however, OS was worse in the group receiving ADT (relative risk LDR BT+ADT Z 2.83, 95%CIZ 1.00-7.98). Furthermore, a trend towardsworse cancer-related survival was observed for the LDR BT+ADT group (p Z 0.095). Conclusions: These results suggest that ADT does not benefit bFFS or OS in IR patients treated with LDR BT. Prospective studies are needed to investigate the role of ADT in IR prostate cancer patients treated with LDR BT. Author Disclosure: J. Rose: None. J.M. Crook: None. Y. Yang: None. A. Warner: None. J. Morris: None. T. Pickles: None. A. Martin: None. E. Vigneault: None. C. Catton: None. G. Rodrigues: None.