Phase 3 Trial of Dose-Escalated Radiation Therapy and Standard Androgen Deprivation Therapy Versus Dose-Escalated Radiation Therapy and Enhanced Androgen Deprivation Therapy With Orteronel for Men With High-Risk Prostate Cancer (NRG/RTOG 1115)

Abstract

Purpose: NRG/RTOG 1115 was a phase 3 trial evaluating the addition of orteronel, a CYP17A1 inhibitor, to radiation therapy (RT) plus androgen deprivation therapy (ADT) in men with high-risk prostate cancer.

Methods and materials: The study was designed to evaluate overall survival for 900 men with high-risk prostate cancer (Gleason 9-10, prostate specific antigen (PSA) > 20, or clinical stage T2 or higher with Gleason ≥ 8). Patients were randomized 1:1 to standard of care (SOC) therapy (RT plus 2 years of ADT) or SOC plus 2 years of orteronel. RT entailed image guided conventionally fractionated dose-escalated external beam RT to the prostate and pelvis to 45 Gy using intensity modulated RT with either intensity modulated RT (to 79.2 Gy) or brachytherapy boost. Health-related quality of life (HRQOL) was measured using the Expanded Prostate cancer Index Composite (EPIC), Patient-Reported Outcome Measurement Information System (PROMIS) fatigue, and EQ-5D. Accrual was halted early because of discontinuation of orteronel development and the trial redesigned to focus on a composite biochemical failure endpoint.

Results: There were a total of 231 eligible randomized patients. Only 29% in the orteronel arm received ≥80% of the planned dose. With median follow-up of 6.2 years, the cumulative incidence of grade 3+ adverse events was higher on orteronel than on the standard arm (P < .001; hazard ratio [HR], 2.32; 95% CI, 1.52-3.47) with 5-year estimates of 59.0% and 35.1%, respectively. No significant differences in overall survival (P = .28; HR, 0.71; 95% CI, 0.39-1.32) or biochemical failure (P = .56; HR, 0.84; 95% CI, 0.47-1.51) were observed. Use of orteronel had a transient negative impact on all prostate cancer-specific QOL domains of the EPIC, but did not increase the magnitude of decline once RT started and had minimal impact on other HRQOL measures.

Conclusions: The addition of orteronel to RT and ADT did not result in significant improvement in any efficacy outcomes, although information was limited by poor drug tolerance and early termination of accrual, thus limiting statistical power.