For the roughly 100,000 men diagnosed annually with intermediate-risk prostate cancer in the United States alone, the choice of radiation schedule carries real-world consequences: fewer treatment days mean less time off work, lower travel burden, and reduced cumulative disruption to daily life. Whether that convenience comes at a cost to quality of life or cancer control has remained a pressing clinical question — one this large international trial was designed to answer directly.
The NRG-GU005 phase 3 randomized trial enrolled patients with localized intermediate-risk prostate cancer (clinical stage T1–T2b, Gleason grade group 1–2, PSA under 20 ng/mL) across 136 centers in the US, Canada, Europe, and Asia between 2017 and 2022, with follow-up extending through October 2024. Participants were allocated 1:1 to stereotactic body radiotherapy (SBRT) delivering 36.25 Gy across just 5 fractions, or to moderately hypofractionated intensity-modulated radiation therapy (MH-IMRT) using a more conventional 20-fraction schedule. Co-primary endpoints included patient-reported urinary irritative/obstructive and bowel quality-of-life outcomes at 2 years via the EPIC-26 instrument, alongside disease-free survival. The trial was powered to detect an 8–10% reduction in clinically meaningful quality-of-life decline and a hazard ratio of 0.62 for disease-free survival.
This trial arrives at a critical inflection point. Prior evidence — including the UK PACE-B trial and pooled analyses from single-institution series — suggested SBRT was non-inferior to conventional fractionation for early-stage prostate cancer, but direct head-to-head comparisons against moderately hypofractionated regimens, now considered standard of care at many centers, have been limited. The NRG-GU005 design is notably rigorous: its international, multi-center scope mitigates institutional bias, and the use of patient-reported rather than physician-graded toxicity endpoints reflects growing recognition that subjective quality of life is the clinically meaningful currency in low-mortality cancers like localized prostate cancer. The key limitation inherent to any prostate cancer radiotherapy trial is follow-up duration — five-year and ten-year biochemical control data will ultimately define the oncologic verdict. This study represents an important infrastructural milestone for ultra-hypofractionation adoption, but the full efficacy and late-toxicity picture remains to be written.