Headline: Relatively low-dose prostate SBRT results in less bowel toxicity at the expense of biochemical control.
The Study: The randomized phase 3 trial NRG-GU005 pitted 5-fraction SBRT (36.25 Gy) against 20–28 fraction IMRT (60–70 Gy) in nearly 700 men with intermediate-risk disease. The co-primary endpoints were patient-reported quality-of-life via EPIC-26 and disease-free survival (DFS). At 2 years, patients receiving SBRT were less likely to experience a clinically meaningful decline (read: a decline of at least 4 points) in bowel function (35% vs 44%), while urinary outcomes were similar. The parallel goal of demonstrating superior DFS for SBRT, on the other hand, didn’t play out so well—in fact, the futility boundary was crossed early. At 3 years, biochemical failures were significantly higher after SBRT (7.8% vs 4.2%). Contrast this with comparable disease outcomes seen in trials such as PACE where the prostate received a higher dose of 40 Gy in 5 fractions. Finally, manufacturers of rectal spacers everywhere have ensured we make space in this blurb to include that enrollees with a rectal spacer in place during treatment with either modality had bowel function scores 2.8 points better on average than those without one.
TBL: Prostate SBRT with expertly-performed simultaneous tumor boost likely strikes a more optimal therapeutic ratio than uniform lower dose delivery, and a moderately hypofractionated simultaneous tumor boost may prove the best of all. | Ellis, ASTRO 2025
The Study: The randomized phase 3 trial NRG-GU005 pitted 5-fraction SBRT (36.25 Gy) against 20–28 fraction IMRT (60–70 Gy) in nearly 700 men with intermediate-risk disease. The co-primary endpoints were patient-reported quality-of-life via EPIC-26 and disease-free survival (DFS). At 2 years, patients receiving SBRT were less likely to experience a clinically meaningful decline (read: a decline of at least 4 points) in bowel function (35% vs 44%), while urinary outcomes were similar. The parallel goal of demonstrating superior DFS for SBRT, on the other hand, didn’t play out so well—in fact, the futility boundary was crossed early. At 3 years, biochemical failures were significantly higher after SBRT (7.8% vs 4.2%). Contrast this with comparable disease outcomes seen in trials such as PACE where the prostate received a higher dose of 40 Gy in 5 fractions. Finally, manufacturers of rectal spacers everywhere have ensured we make space in this blurb to include that enrollees with a rectal spacer in place during treatment with either modality had bowel function scores 2.8 points better on average than those without one.
TBL: Prostate SBRT with expertly-performed simultaneous tumor boost likely strikes a more optimal therapeutic ratio than uniform lower dose delivery, and a moderately hypofractionated simultaneous tumor boost may prove the best of all. | Ellis, ASTRO 2025