• Yasir Alayed, Patrick Cheung, Danny Vesprini, Stanley Liu, William Chu, Hans Chung, Hima Bindu Musunuru, Melanie Davidson, Ananth Ravi, Ling Ho, Andrea Deabreu, Laura D'Alimonte, Zeeba Bhounr, Liying Zhang, Kristina Commisso, and Andrew Loblaw.
• Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Canada; Division of Radiation Oncology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
• Int. J. Radiat. Oncol. Biol. Phys. 2019 May 1; 104 (1): 36-41.

PurposeThere is limited data on stereotactic ablative radiation therapy (SABR) in high-risk prostate cancer (PCa), especially regarding the role of elective nodal irradiation (ENI). This study compares 2 prospective phase 2 trials using SABR in high-risk PCa, with and without ENI.Methods And MaterialsPatients had high-risk PCa. Those in trial 1 received 40 Gy in 5 fractions to the prostate and 30 Gy in 5 fractions to the seminal vesicles. Patients in trial 2 received 40 Gy in 5 fractions to the prostate and 25 Gy in 5 fractions to the pelvis and seminal vesicles. National Cancer Institute Common Terminology Criteria for Adverse Events toxicities were collected. Biochemical failure (BF) was defined as nadir + 2, and the 4-year prostate-specific antigen (PSA) response rate (4yPSARR) was <0.4 ng/mL.ResultsSixty patients were included (trial 1, n = 30; trial 2, n = 30). Median follow-up was 5.6 years and 4.0 years. The median nadir PSA was 0.02 ng/mL for both trials. Six patients had BF, all from trial 1. The BF rate was 14.6% at 5 years in trial 1 and 0% in trial 2. Sixty-three percent of patients in trial 1 and 93% in trial 2 had a 4yPSARR. Two patients died in trial 1, 1 from metastatic disease. One patient in trial 2 died of other causes. No other patients developed metastatic disease, and 1 patient in trial 1 had castrate resistant PCa. Overall survival at 5 years was 93.2% and 96.7% (P = .86). There was significantly worse late gastrointestinal and sexual toxicity in trial 1, but there was no difference in late genitourinary toxicity.ConclusionsSABR in high-risk PCa yields biochemical control rates that may be comparable to that of other radiation therapy modalities. ENI using SABR is feasible and may lead to a significant improvement in biochemical control and in 4yPSARR, without an increase in late gastrointestinal or genitourinary toxicity. Longer follow-up would provide a better assessment of biochemical control. Well-conducted phase 3 trials are needed to fully establish the role of SABR and ENI in high-risk PCa.Copyright © 2018 Elsevier Inc. All rights reserved.

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