Short-Course Radiation Eases Side Effects but Not Cancer Control in Prostate Cancer

Results from the international phase III NRG Oncology GU005 trial presented at the American Society for Radiation Oncology (ASTRO) 2025 Annual Meeting indicate that delivering radiation for localized, intermediate-risk prostate cancer in just five sessions reduced side effects but did not outperform longer treatment in disease control.

Patients receiving stereotactic body radiation therapy (SBRT) reported fewer declines in bowel, urinary, and sexual function than those treated with moderately hypofractionated radiation. However, SBRT patients were more likely to show rising prostate-specific antigen (PSA) levels.

"These findings provide important new evidence to help guide treatment decisions for patients with localized prostate cancer," said Rodney Ellis, MD, the trial’s principal investigator and professor of radiation oncology at the University of South Florida/Tampa General Hospital. "The results help clarify what patients can expect from shorter versus longer courses of radiation therapy and enable more personalized treatment decisions."

Key Highlights

The study enrolled 698 men with untreated, intermediate-risk prostate cancer between 2017 and 2022. Patients were randomized to SBRT (36.25 Gy in 5 sessions) or moderately hypofractionated radiation (20–28 sessions).

At two years, SBRT patients had lower rates of bowel function decline (35% vs. 44%) and urinary incontinence (26% vs. 35%). Sexual function initially favored SBRT at one year but was similar at two years.

For disease-free survival, 88.6% of SBRT patients were progression-free at three years, compared with 92.1% for standard therapy. The gap was largely due to higher PSA failures with SBRT (7.8% vs. 4.2%).

"The PSA findings require careful interpretation," said Dr. Ellis. "With larger doses per fraction, patients can experience temporary PSA ‘bounces’ that may not signal true progression. Five-year follow-up will tell us more."

Overall survival was 97% in both groups at three years, with rare severe urinary complications (0.6% with SBRT vs. 2.5% with standard therapy). Rectal spacers reduced bowel side effects across both arms.

The trial used a slightly lower SBRT dose than other recent studies, which may explain differences in PSA outcomes. Longer follow-up is expected to clarify whether higher SBRT doses balance cancer control with quality of life.

Dr. Ellis said future trials will explore SBRT for higher-risk patients and refine ways to reduce side effects. For now, he emphasized that patients face a meaningful choice: shorter, more convenient therapy with improved quality of life, or longer treatment with stronger biochemical control.

"Patients have different priorities and values when it comes to their care," he said. "These results help inform those deeply personal decisions."