How Many Radiotherapy Sessions for Prostate Cancer? ASTRO 2026 Recommendations
ASTRO’s 2026 guideline supports shorter radiotherapy schedules for localized prostate cancer. Explore 20–28 sessions, five-fraction SBRT, patient selection and side effects.
Short answer: Suitable patients who choose radiotherapy for localized prostate cancer may complete treatment in fewer sessions than with conventional schedules. The update announced by ASTRO on October 27, 2026 favours moderate hypofractionation over conventional fractionation across all risk groups and strengthens the role of five-fraction SBRT in appropriate low- and intermediate-risk patients. The number of sessions alone does not determine suitability or treatment success. [1]
Fewer hospital visits can be an important practical benefit for patients and families. Decisions must nevertheless consider disease risk, baseline urinary function, the treatment area and the characteristics of the technique used.
Which patients does the new ASTRO guideline cover?
The update concerns localized prostate cancer without lymph-node or distant metastases — N0M0 — treated with external beam radiotherapy as the initial local treatment. It covers low-risk patients who decline active surveillance, along with intermediate-, high- and very high-risk patients who choose radiotherapy.
These recommendations should therefore not be directly generalized to adjuvant or salvage radiotherapy after prostate surgery, or radiation treatment for metastatic disease. [2]
Published in Practical Radiation Oncology, the guideline replaces the 2018 hypofractionation recommendations. ASTRO developed it in collaboration with ASCO, AUA, ESTRO and SUO. It provides treatment recommendations based on clinical evidence rather than approval of a new drug or device. [1, 2]
What do hypofractionation and SBRT mean?
A fraction is a portion of the radiotherapy dose, usually corresponding to one treatment session in everyday language.
Moderate hypofractionation reduces the total number of sessions by using a higher dose per session. Ultrahypofractionation uses still fewer sessions with higher individual doses; SBRT is a common example in prostate cancer.
Fewer sessions do not mean that the total dose is reduced by the same proportion. Dose per session, total dose, the target area and protection of surrounding organs are planned together.
What are the main ASTRO 2026 recommendations?
| Clinical situation or approach | Main recommendation | Meaning for patients |
|---|---|---|
| Moderate hypofractionation | Preferred over conventional fractionation across all risk groups choosing radiotherapy for localized disease. | A suitable shorter schedule should be discussed as an alternative to longer treatment. |
| SBRT in low-risk disease | An option for patients who decline active surveillance and choose external beam radiotherapy. | Discuss the need for treatment and active surveillance first. |
| SBRT in intermediate-risk disease | One of the recommended options for suitable patients. | Patient selection and target volume remain important. |
| SBRT in high- and very high-risk disease | Conditional recommendation. | Not an automatic choice for every patient. |
| Substantial baseline urinary symptoms | Moderate hypofractionation is conditionally preferred over ultrahypofractionation. | Assess urinary function before choosing five fractions. |
These recommendations concern schedule selection after a decision to use radiotherapy. They do not mean that every patient with prostate cancer should start radiation treatment. [1]
Does radiotherapy take 20–28 sessions or five sessions?
The phrase “20–28 sessions” does not mean that every number within that range is equally appropriate. The guideline describes specific dose and fractionation schedules.
| Approach | Example number of sessions | Approximate treatment period |
|---|---|---|
| Conventional fractionation | 37–39 sessions | Approximately 7–8 weeks |
| Moderate hypofractionation | 20 or 28 sessions | Approximately 4–6 weeks |
| Five-fraction SBRT | 5 sessions | Usually 1–2 weeks |
These examples help compare treatment approaches. Preparation, planning and the individual treatment timetable require separate consideration. Five fractions do not necessarily mean five consecutive days. [1, 3, 4]
Does shorter treatment reduce cancer control?
CHHiP is one of the key trials supporting moderate hypofractionation. This randomized phase 3 study found that 60 Gy in 20 fractions was non-inferior to the conventional schedule of 74 Gy in 37 fractions for disease control. Long-term side-effect findings also supported this schedule.
Importantly, not all shorter regimens tested in the same study achieved the same result. Fewer sessions do not make every schedule equivalent. Evidence must be interpreted alongside the specific doses and schedules studied. [3]
PACE-B provides important randomized evidence for five-fraction SBRT. It assigned 874 patients to SBRT or control radiotherapy. At five years, freedom from biochemical or clinical failure was 95.8% with SBRT and 94.6% with control treatment, demonstrating non-inferiority.
This does not establish longer survival with SBRT or superiority across all risk groups. The findings must be interpreted within the trial’s patient-selection criteria. [4]
Does five-fraction treatment have fewer side effects?
Reducing the number of sessions does not necessarily reduce side effects.
In PACE-B, the cumulative incidence of late grade 2 or higher urinary toxicity up to five years was 26.9% with SBRT and 18.3% with control radiotherapy. These percentages do not mean that the same proportion of patients still had symptoms at the five-year visit; they describe events arising during follow-up.
A favourable cancer-control result can coexist with a different pattern of side effects. Patients should be informed about expected effectiveness and potential urinary, bowel and sexual effects. [4]
What matters for patients with urinary symptoms?
Patients with substantial urinary symptoms at baseline should have their urinary function assessed before a five-fraction schedule is selected. The update conditionally recommends moderate hypofractionation over ultrahypofractionation for this group.
This does not mean that everyone with urinary symptoms is unsuitable for radiotherapy. Rather, it is a distinction that may influence the choice of radiation schedule. [1]
Are hormone treatment and lymph-node irradiation shortened too?
Radiotherapy fractionation and the need for, or duration of, hormone treatment are separate decisions. Planning five radiation sessions does not mean that androgen-deprivation therapy is unnecessary or finishes with the fifth session.
Irradiating the prostate and electively treating pelvic lymph nodes also involve different target volumes. ASTRO conditionally recommends ultrahypofractionation for elective pelvic nodal treatment only within a clinical trial. This is particularly relevant in high-risk disease. [1]
Does short-course radiotherapy replace active surveillance?
No. Active surveillance remains an important approach for suitable patients with low-risk prostate cancer. The availability of a more convenient treatment does not, by itself, create a need for treatment.
Active surveillance is also different from leaving cancer unmonitored. It uses structured follow-up with PSA testing, clinical assessment, appropriate imaging and repeat biopsy when indicated. [5]
Does this change the choice between surgery and radiotherapy?
Fewer hospital visits may matter to a patient considering radiotherapy. However, this guideline is not a comparison demonstrating that short-course radiotherapy is superior to radical prostatectomy.
A decision should not rest solely on the number of treatment days. Cancer characteristics, life expectancy, general health, existing urinary and sexual function, and patient priorities should be considered together. Discussion with both urology and radiation oncology teams can help clarify suitable options.
Editorial assessment
The main value of the ASTRO 2026 update is its stronger support for schedules that can reduce the time and travel burden of radiotherapy while maintaining disease control in suitable patients. This may be especially relevant for people who must travel frequently to a treatment centre.
Shorter does not mean better for every patient. Strong evidence for moderate hypofractionation should be explained alongside SBRT patient selection and differences in side-effect profiles. Treatment recommendations should aim to preserve both cancer control and quality of life, rather than simply reduce the number of sessions.
Frequently asked questions
Is five-fraction SBRT suitable for everyone?
No. Disease risk, baseline urinary function, the target area and the ability to plan treatment safely must be assessed.
Is all treatment finished after the fifth session?
Not always. Hormone treatment, if needed, may continue longer. PSA and clinical follow-up also continue after radiotherapy.
Does a higher dose with SBRT mean better outcomes?
A higher dose per session does not establish superiority on its own. Total dose, scheduling and protection of surrounding organs all matter.
Should I change my schedule if I am already receiving radiotherapy?
This news is not a reason to change a treatment already started on your own. Discuss questions about the existing plan with your treating radiation oncologist.
Sources
- ASTRO updates guideline on shorter-course radiation therapy for localized prostate cancer. October 27, 2026 [Internet]. Available from: 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
- Hypofractionated Radiation Therapy for Localized Prostate Cancer: An ASTRO Clinical Practice Guideline. Practical Radiation Oncology. 2026. doi:10.1016/j.prro.2026.09.017
- Conventional versus hypofractionated high-dose intensity-modulated radiotherapy for prostate cancer: 5-year outcomes of the randomised, non-inferiority, phase 3 CHHiP trial. Lancet Oncology. 2016;17(8):1047–1060. doi:10.1016/S1470-2045(16)30102-4 · PubMed · PMC
- Phase 3 Trial of Stereotactic Body Radiotherapy in Localized Prostate Cancer. New England Journal of Medicine. 2024;391(15):1413–1425. doi:10.1056/NEJMoa2403365 · PubMed
- EAU Guidelines on Prostate Cancer — Treatment. Accessed November 1, 2026 [Internet]. Available from: https://uroweb.org/guidelines/prostate-cancer/chapter/treatment
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