What Is SBRT for Prostate Cancer?

SBRT is a type of radiation therapy that allows many prostate cancers to be treated in approximately five sessions.

When patients hear this for the first time, the reaction is usually immediate:

“How can five treatments work as well as a treatment that takes several weeks?”

It is a reasonable question. For many years, radiation therapy for prostate cancer was typically delivered in 38 to 44 treatments. Later, shorter schedules of 20 to 28 treatments became common. SBRT represents a further evolution, allowing treatment to be completed in a much smaller number of sessions.

The reason this is possible is related to both the biology of prostate cancer and major technological advances in radiation oncology.

Unlike many other tumors, prostate cancer appears to respond particularly well to higher doses delivered in each treatment session. This concept has been studied for years and helped pave the way for increasingly shorter treatment schedules.

At the same time, the precision of radiation therapy has improved dramatically. Today, we routinely use CT imaging, MRI, image-guided radiation therapy, and daily verification techniques to localize the prostate with a very high degree of accuracy before each treatment.

For that reason, SBRT is not simply a matter of delivering more radiation in fewer days. It requires a significantly higher level of precision than many conventional radiation treatments.

One of the most important questions is whether reducing the number of treatments compromises effectiveness.

So far, the available evidence suggests that it does not.

PACE-B, one of the most important clinical trials in this field, compared SBRT with conventional or moderately hypofractionated radiation therapy in patients with localized prostate cancer.

The study demonstrated comparable cancer control rates between the treatment groups. In practical terms, completing radiation therapy in five sessions did not result in a lower likelihood of controlling the disease.

Patients also frequently ask whether delivering a higher dose per treatment increases the risk of side effects.

Modern studies have shown favorable outcomes when SBRT is delivered using appropriate technology, strict quality assurance procedures, and careful patient selection.

That does not mean SBRT is the best option for everyone.

Factors such as cancer risk group, prostate size, pre-existing urinary symptoms, prior procedures, and other medical conditions may influence the decision.

For that reason, treatment recommendations should always be individualized.

Today, major professional organizations consider SBRT a standard treatment option for many patients with localized prostate cancer.

If I had to summarize the concept in a single sentence, it would be this:

SBRT allows prostate cancer to be treated in approximately five sessions using highly precise radiation therapy, with cancer control outcomes comparable to those achieved with substantially longer treatment schedules in appropriately selected patients.

References

Brand DH, Tree AC, Ostler P, et al. Intensity-modulated fractionated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): acute toxicity findings from an international, randomised, open-label, phase 3, non-inferiority trial. Lancet Oncology. 2019;20(11):1531-1543. doi:10.1016/S1470-2045(19)30569-8

Morgan SC, Hoffman K, Loblaw DA, et al. Hypofractionated Radiation Therapy for Localized Prostate Cancer: Executive Summary of an ASTRO, ASCO, and AUA Evidence-Based Guideline. Practical Radiation Oncology. 2018;8(6):354-360. doi:10.1016/j.prro.2018.08.002