ASCO 2017: Stereotactic ablative radiation therapy for the treatment of oligometastatic prostate cancer

Chicago, IL ( Over the past several years, there has been increased interest in treatment of oligometastatic sites for patients with prostate cancer. At the prostate cancer poster session at the 2017 ASCO annual meeting, Dr. Phuoc Tran presented their findings of stereotactic ablative radiation therapy for treatment of oligometastatic prostate cancer. Stereotactic ablative radiotherapy (SABR) is highly focused, high-dose radiation that is well suited for treatment of oligometastases.

This study included 84 men who satisfied criteria of oligometastatic disease diagnosed on imaging who underwent consolidative SABR. Variables collected included demographic, clinical, toxicity, and efficacy information. For this analysis, the first 66 men who were followed for a minimum of 4.5 months were included. SABR was delivered in 1-5 fractions of 5-18 Gy. Outcomes assess included local progression-free survival (LPFS), biochemical progression-free survival (bPFS, defined as PSA nadir + 2), distant progression free survival (DPFS), ADT-free survival (ADT-FS), and time to next intervention (TTNI).

Among the 66 men included, 38% presented with synchronous metastatic disease and the remaining patients had recurrent oligometastases. Median age was 65 years (47-84) and 26% were CRPC. The median pre-SABR was 1.2 ng/mL (range: <0.1 – 96) and SABR was delivered to 134 metastases: 89 bone (66%), 40 to lymph nodes (30%), and 5 (4%) visceral metastases. Overall, LPFS at 1-year was 92%, while the bPFS and DPFS at 1-year were 69% and 69%, respectively. Median TTNI was not reached yet in this cohort. Among the 18 men with hormone sensitive prostate cancer who had their ADT deferred, 56% remain free of disease following SABR (1-year ADT-FS of 78%) and in 17 CRPC patients, 11 had > 50% PSA declines with 1-year TTNI of 30% over a median of 45 weeks. Crude Grade 1 and 2 acute toxicities were 36% and 11% respectively, with no Grade > 2 toxicity.

In conclusion, although this is a small, highly selected cohort, the results presented here are encouraging, demonstrating consolidative SABR for oligometastatic prostate cancer is feasible and well-tolerated. Following prospective validation, SABR may be considered as part of the treatment armamentarium for patients with advanced disease. More definitive conclusions await the completion of prospective randomized trials, such as the Belgian STOMP and the Baltimore ORIOLE trials.

Presented By: Phuoc T. Tran, MD, PhD, Johns Hopkins University School of Medicine, Baltimore, MD, USA

Co-Authors: C. Leigh Moyer, Ryan Phillips, Noura Radwan, Ashley Ross, Diane K. Reyes, Jean Wright, Emmanuel S. Antonarakis, Daniel Y. Song, Curtiland Deville, Patrick C. Walsh, Theodore L. DeWeese, Michael Anthony Carducci, Edward M. Schaeffer, Kenneth J. Pienta, Mario A. Eisenberger

Written By: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre
Twitter: @zklaassen_md

at the 2017 ASCO Annual Meeting - June 2 - 6, 2017 – Chicago, Illinois, USA