ASTRO Guideline Backs Hypofractionation Across Risk Groups in Localized Prostate Cancer

Moderate hypofractionation is now recommended over conventional fractionation for patients with localized prostate cancer in every risk group who elect definitive external beam radiation therapy (EBRT), and ultrahypofractionation is recommended as a standard option for many patients, including those with intermediate-risk disease, according to an updated clinical practice guideline from the American Society for Radiation Oncology (ASTRO).^1,2

The guideline, published in Practical Radiation Oncology, replaces ASTRO's 2018 recommendations.¹ Since 2010, 11 randomized trials enrolling more than 7000 patients have compared moderate hypofractionation with conventional fractionation, and long-term follow-up from these studies has shown similar cancer control, adverse effect (AE) profiles, and quality of life with either approach.²

Ultrahypofractionation is most often delivered as stereotactic body radiation therapy (SBRT), which lets patients finish treatment in 5 sessions over 1 to 2 weeks.¹

"SBRT has moved from a promising alternative to a standard treatment option for many patients with localized prostate cancer," Scott C. Morgan, MD, chair of the guideline task force, a radiation oncologist at The Ottawa Hospital, and a professor of radiation oncology at the University of Ottawa, said in a news release. "These recommendations give clinicians clear direction on using shorter-course treatment safely while preserving the excellent outcomes patients expect from definitive radiation therapy."

How does hypofractionation differ from conventional fractionation?

Hypofractionated EBRT increases the radiation dose given at each visit so that the full course can be completed in fewer sessions, with an overall therapeutic effect similar to that of conventional fractionation. Moderate hypofractionation is generally given over 4 to 6 weeks.

The guideline defines moderate hypofractionation as fraction sizes of 240 to 340 cGy and ultrahypofractionation as fraction sizes of at least 500 cGy.² The task force drew a distinction between the 2 terms: ultrahypofractionation describes fraction size alone, whereas SBRT is a high-precision subset that relies on advanced imaging, image guidance, motion management, and highly conformal delivery. Compared with conventional fractionation, moderate hypofractionation removes 9 to 24 fractions, or 2 to 5 weeks, from a treatment course.

Which patients are candidates for moderate hypofractionation?

Moderate hypofractionation is recommended over conventional fractionation for treatment of the prostate, with or without the seminal vesicles, in all risk groups, irrespective of patient age, comorbidity, anatomy, or urinary function.¹ The decision to add androgen deprivation therapy should be made separately from the choice of fractionation schedule.

For patients receiving elective pelvic nodal radiation, the guideline recommends moderate hypofractionation to the prostate delivered alongside conventional or near-conventional fractionation to the pelvic lymph nodes within a single-phase plan.

Which patients are candidates for ultrahypofractionation?

Ultrahypofractionated EBRT is recommended as a treatment option for patients with intermediate-risk disease receiving radiation to the prostate and seminal vesicles, and for those with low-risk disease who forgo active surveillance in favor of EBRT. In high-risk or very high-risk disease, the recommendation for ultrahypofractionation is conditional.

Patients with substantial baseline urinary symptoms represent an exception; for this group, moderate hypofractionation is conditionally recommended over ultrahypofractionation because larger fraction sizes may heighten the risk of treatment-related urinary AEs. The guideline notes that an International Prostate Symptom Score of 15 to 20 or higher is often cited as the threshold for significant symptoms, although clinical judgment should ultimately guide the decision.² Ultrahypofractionation for elective pelvic nodal treatment is conditionally recommended only within a clinical trial.¹

What dose schedules are recommended?

For moderate hypofractionation, recommended prostate doses are 60 to 62 Gy in 20 fractions or 70 Gy in 28 fractions.² For ultrahypofractionation, 36.25 to 40 Gy in 5 fractions is conditionally recommended, and regimens using fewer than 5 fractions are not recommended outside a clinical trial. The guideline also conditionally recommends delivering 5-fraction ultrahypofractionation on nonconsecutive days over approximately 2 weeks.

What do the recommendations say about target volumes and treatment delivery?

Treatment of the prostate alone is recommended for patients with low-risk disease who decline active surveillance, whereas coverage of at least part of the seminal vesicles is recommended or conditionally recommended for higher-risk disease, depending on clinical risk.¹ Selected patients with a dominant lesion visible on MRI may be considered for a focal intraprostatic boost.

The guideline's planning and delivery recommendations center on precision, including MRI-informed planning when appropriate, daily motion management, and intensity-modulated radiation therapy. Intrafraction tracking is conditionally recommended for patients receiving ultrahypofractionation, and the use of rectal spacers is framed as a shared decision between physician and patient.

"The evidence supporting hypofractionation is now much stronger in the years since ASTRO's previous guideline was published," Karen Hoffman, MD, MPH, FASTRO, vice chair of the task force, a professor of radiation oncology, and medical director of the Mays Radiation Oncology Center at The University of Texas MD Anderson Cancer Center, said in the release. "This guideline also reflects how treatment planning has evolved, including greater use of daily image guidance and more precise approaches to managing motion during treatment."

References

1. ASTRO updates guideline on shorter-course radiation therapy for localized prostate cancer. News release. American Society for Radiation Oncology. October 27, 2026. Accessed October 28, 2026. https://www.astro.org/news-and-publications/news-and-media-center/news-releases/2026/astro-updates-guideline-on-shorter-course-radiation-therapy-for-localized-prostate-cancer
2. Morgan SC, Halthore A, Jia AY, et al. Hypofractionated radiation therapy for localized prostate cancer: an ASTRO clinical practice guideline. Pract Radiat Oncol. Published online October 27, 2026. doi:10.1016/j.prro.2026.09.017