September 29 2025
Results of the NRG Oncology NRG-GU005 clinical study comparing stereotactic body radiation therapy (SBRT) to moderately hypofractionated intensity-modulated radiation therapy (MH-IMRT) for patients with localized intermediate risk prostate cancer indicate that the use of SBRT improved bowel health related quality of life (HRQOL) in this patient population. There was no significant improvement seen for the other primary objectives including urinary HRQOL and there was a lack of improvement in distant-free survival for patients. These results were recently reported during the Plenary Session of the American Society for Radiation Oncology Annual Meeting in San Francisco, California.
“We are pleased NRG-GU005 was able to meet the EPIC-26 Bowel domain QOL endpoint per the co-primary endpoints of NRG-GU005. While the Urinary irritative or obstructive domain of EPIC-26 was not able to show a significant improvement, the secondary genitourinary endpoints for lower incontinence related quality of life and improved maintenance of erectile dysfunction versus moderately hypo fractionated IMRT were also significant as presented by Dr. James Yu on Monday’s session. While the Disease-Free Survival (DFS) co-primary endpoints crossed futility for superiority at three years due solely to higher biochemical failure by PSA, further follow up is warranted to see the results at 5 years or more. PACE-B showed SBRT is non-inferior to IMRT, and now NRG-GU005 shows SBRT can be less likely to detrimentally effect patients’ quality of life as determined by these patient reported outcomes,” stated Rodney J. Ellis, MD, from the University of South Florida and the lead author of the NRG-GU005 abstract.
The Phase III NRG-GU005 trial enrolled 698 evaluable patients with immediate-risk prostate cancer. Trial participants were randomly assigned to either receive SBRT at 36.25 Gy in 5 fractions or to receive IMRT at 70 Gy in 28 fractions or 60 Gy in 20 fractions. The HRQOL co-primary endpoint was designed to show 10% and 8% absolute reductions in the frequency of a minimal clinically important decline (MCID) in bowel and urinary irritation or obstruction domains respectively at 24 months. The Expanded Prostate Cancer Index Composite (EPIC-26) questionnaire was distributed and completed at baseline, 12- and 24-months post-treatment. At 2 years post-treatment, 82.5% of patients who received MH-IMRT completed the EPIC versus 85.1% of patients who received SBRT and approximately 97.5% and 96.2% of the questionnaires received had scorable bowel and UID domains, respectively.
Fewer patients on the SBRT arm experienced MCID in bowel HRQOL at 2 years than patients receiving IMRT (34.9% vs. 43.8%, p=0.034). Longitudinal bowel domain scores and use of rectal spacers further increased favorability of SBRT over IMRT. However, there was no significant difference in MCID frequency for the urinary irritative or obstructive symptoms domain between patients receiving SBRT or IMRT (33.7% vs. 34.7%, p=0.68). Additionally, the interim analysis of this study crossed the futility boundary for DFS, thus indicating SBRT is not superior over hypofractionated IMRT in this patient population.
This project was supported by grants UG1CA189867 (NCORP), U10CA180868 (NRG Oncology Operations), U10CA180822 (NRG Oncology SDMC), U24CA180803 (IROC), CTEP from the National Cancer Institute (NCI).
Special Podcast Episode
Follow The NRG Oncology Podcast on Spotify, Apple Podcasts, and YouTube for a special episode interviewing Dr. Rodney Ellis on the findings of the 2025 ASTRO Plenary Session Presentation for NRG-GU005. Podcast information and playable episodes are available on the NRG website as well.
Citation
Ellis RJ, Pugh SL, Yu JB, Feng FY, Konski AA, Grubb III RL, Wallace RE, Gladstone DJ, Ménard C, Frazier AJ, Pennington JD, Michalski JM, Spratt DE, Martinez A, Morgan SC, Mihai A, Paulus R, Sander HM. Primary results from NRG-GU005: A Phase III Trial of SBRT vs. Hypofractionated IMRT for Localized Intermediate Risk Prostate Cancer. Paper presented during the Plenary Session at the annual meeting of the American Society for Radiation Oncology. San Francisco, CA. (2025, September-October).
About NRG Oncology
NRG Oncology conducts practice-changing, multi-institutional clinical and translational research to improve the lives of patients with cancer. Founded in 2012, NRG Oncology is a Pennsylvania-based nonprofit corporation that integrates the research of the legacy National Surgical Adjuvant Breast and Bowel Project (NSABP), Radiation Therapy Oncology Group (RTOG), and Gynecologic Oncology Group (GOG) programs. The research network seeks to carry out clinical trials with emphasis on sex-specific malignancies, including gynecologic, breast, and prostate cancers, and on localized or locally advanced cancers of all types. NRG Oncology’s extensive research organization comprises multidisciplinary investigators, including medical oncologists, radiation oncologists, surgeons, physicists, pathologists, and statisticians, and encompasses more than 1,300 research sites located world-wide with predominance in the United States and Canada. NRG Oncology is supported primarily through grants from the National Cancer Institute (NCI) and is one of five research groups in the NCI’s National Clinical Trials Network. www.nrgoncology.org