SBRT for Oligometastatic Prostate Cancer: Known and Still Being Studied

Short answer: Stereotactic body radiation therapy (SBRT) can precisely treat a small number of prostate cancer metastases and may delay progression for selected patients. It is not a proven replacement for systemic therapy, and ongoing phase 3 trials are still defining whether it improves major long-term outcomes in the modern PSMA PET era.

What does “oligometastatic” mean?

Oligometastatic describes cancer with a limited number of visible metastatic sites—often three to five in clinical trials. It can appear:

• when prostate cancer is first diagnosed;
• after surgery or prostate radiation, called oligorecurrence; or
• while cancer is already being controlled with hormone therapy.

These are biologically and clinically different situations. A result from one group should not automatically be applied to another.

What is metastasis-directed SBRT?

SBRT delivers a highly focused dose to each visible metastasis, often in one to five treatments. The goal may be to:

• achieve durable control at treated sites;
• delay appearance of additional disease;
• postpone a change in systemic therapy;
• prevent symptoms from a high-risk lesion; or
• complement hormone therapy and treatment of the prostate or prostate bed.

SBRT treats what can be seen. It cannot sterilize microscopic cancer cells elsewhere in the body.

What evidence supports this approach?

Randomized phase 2 studies such as STOMP and ORIOLE helped establish that metastasis-directed treatment can delay progression or the start of androgen-deprivation therapy in selected people with recurrent hormone-sensitive prostate cancer.

More recent research is examining SBRT with modern systemic therapy. The phase 2 ARTO trial studied people with oligometastatic castration-resistant disease receiving abiraterone and androgen-deprivation therapy. Adding SBRT improved the trial's earlier biochemical response endpoint. A 2026 unplanned long-term analysis explored overall survival, but an unplanned analysis should be considered hypothesis-strengthening rather than definitive phase 3 proof.

What do guidelines say?

The AUA/ASTRO/SUO salvage guideline says clinicians may perform stereotactic ablative radiotherapy for regional or metastatic oligorecurrence, but should discuss the benefits and toxicity risks. This is a conditional recommendation, reflecting limited high-level evidence and the need for careful selection.

Treatment decisions also depend on:

• whether the disease is hormone-sensitive or castration-resistant;
• whether metastases appeared at diagnosis or later;
• PSA doubling time and other risk features;
• PSMA PET findings;
• prior radiation and normal-tissue dose;
• symptoms and lesion location; and
• systemic treatment options.

Which phase 3 questions remain open?

The 2026 METRO publication is a trial protocol, not a results report. METRO is comparing modern standard care with or without metastasis-directed SBRT for one to three PSMA PET-detected metastases. Its primary endpoint is biochemical progression-free survival, and study completion is years away.

SPARKLE is another phase 3 trial evaluating whether adding different intensities of systemic therapy to metastasis-directed treatment improves longer-term disease control in oligorecurrent hormone-sensitive prostate cancer.

These studies are important because imaging now finds smaller deposits and systemic therapy has improved. Older evidence may not fully answer how much SBRT adds to today's standard care.

Potential benefits and risks

Possible benefits include high control of treated lesions, delaying progression, and postponing a systemic treatment change. Risks depend on where the lesion is located and can include fatigue, pain flare, fracture, bowel or urinary effects, nerve injury, or damage to nearby organs. Serious toxicity is uncommon with careful planning but is not zero.

Repeat SBRT also requires review of prior radiation plans to avoid exceeding normal-tissue tolerance.

Questions for a multidisciplinary discussion

1. Is my disease truly limited on the best available imaging?
2. What is the goal: delay, symptom prevention, local control, or longer survival?
3. What systemic therapy is recommended with SBRT?
4. Is there evidence for my exact disease state?
5. Could a clinical trial answer the question more reliably?
6. What are the site-specific risks?

Metastasis-directed SBRT is a promising and increasingly used strategy. The most accurate description in 2026 is that it can help selected patients, while definitive evidence for several disease settings is still maturing.

Questions patients often ask

Can SBRT eliminate metastatic prostate cancer?

SBRT can achieve high control of treated lesions, but untreated microscopic disease may remain. It should not be described as a guaranteed cure for metastatic prostate cancer.

Does SBRT replace hormone therapy?

Usually no. The role of hormone therapy depends on whether disease is newly metastatic or recurrent, hormone-sensitive or castration-resistant, and other risk factors. Trials are actively testing the best combinations.

How many metastases can be treated?

Trials use different limits, often three to five visible lesions. Number alone is not enough; location, size, prior treatment, imaging, symptoms, and overall disease behavior all matter.

Sources and further reading

1. Salvage Therapy for Prostate Cancer: AUA/ASTRO/SUO Guideline Part III. The Journal of Urology (2024).
2. Metastasis-directed SBRT for oligometastatic hormone-sensitive prostate cancer (METRO). BMC Cancer (2026).
3. SBRT plus abiraterone and ADT in oligometastatic castration-resistant prostate cancer (ARTO). The Lancet Oncology (2026).
4. Metastasis-directed Therapy for Oligorecurrent Prostate Cancer (SPARKLE). ClinicalTrials.gov (2026).