Radiation Therapy in the Definitive Management of Oligometastatic Prostate Cancer: The Johns Hopkins Experience

Purpose: The use of radiation therapy (RT) in consolidating oligometastatic prostate cancer (OPCa) is a rapidly evolving treatment paradigm. We review our institutional experience using metastasis-directed therapy in the definitive management of men with OPCa. Methods and Materials: Patients with OPCa treated with definitive RT were included. The Kaplan-Meier method and multivariable Cox regression analysis were performed to assess biochemical progression-free survival (bPFS) and time to next intervention. Cumulative incidence functions were used to calculate rates of local failure. Toxicity was assessed using Common Terminology Criteria for Adverse Events (version 4). Results: This study analyzed 156 patients with OPCa and 354 metastatic lesions with median follow-up of 24.6 months. Of 150 patients with toxicity data, 53 (35%) experienced acute grade 1 toxicity, 8 (5%) had grade 2, and none had grade 3 toxicity. Only 13 patients (9%) had late toxicities. At 24 months, the cumulative incidence of local failure was 7.4%. Median bPFS for the entire cohort was 12.9 months and 52% at 1 year. On multivariable analysis, factors associated with prolonged bPFS were peri-RT androgen deprivation therapy (ADT), lower gross tumor volume, and hormone-sensitive (HS) OPCa. Median time to next intervention, including repeat RT, was 21.6 months. Median bPFS for men with HS prostate cancer was 17.2 months compared with 7.2 months in men with castrate-resistant OPCa (P <.0001), and cumulative incidence of local failure at 24 months was lower with HS OPCa (4.8% vs 12.1%; P =.034). We analyzed 28 men with HS OPCa treated with a course of peri-RT ADT (median, 4.3 months) with recovery of testosterone. At a median follow-up of 33.5 months, 20 patients had not developed bPFS, median bPFS had not been reached, and 24-month bPFS was 77%. Conclusions: Metastasis-directed therapy can be effective across a wide range of OPCa subtypes, but with differential efficacy. Further study is warranted to investigate the use of RT across the wide range of patients with OPCa.