Multicenter randomized phase 2 trial of addition of SBRT to abiraterone and ADT in oligometastatic CRPC: long-term OS analysis of ARTO

The randomized phase 2 ARTO trial, at 16 centers in Italy, showed improved early clinical outcomes with adding metastasis-directed stereotactic body radiotherapy (SBRT) to abiraterone acetate and androgen deprivation therapy (ADT) in oligometastatic castration-resistant prostate cancer (CRPC). Unplanned overall survival (OS) analysis of the trial has now been published. The trial included 157 adult patients who had no more than three metastatic sites and had received no previous systemic therapy for metastatic CRPC. The patients were randomized 1:1 to SBRT plus abiraterone acetate and ADT (experimental group; n=75) or abiraterone acetate plus ADT (control group; n=82). After a median follow-up of 53 months (IQR 43-60), median OS was 50 months in the control group versus not reached in the experimental group (HR 0.55; p=0.021). Most common grade 3-4 adverse events were infectious complications (five in the control group versus none in the experimental group) and cardiovascular disorders (three in the control group versus three in the experimental group. One treatment-related death occurred in the control group due to myocardial failure. The authors conclude that the ARTO trial showed significant OS benefit with the addition of metastasis-directed SBRT to systematic therapy for oligometastatic CRPC.