Single-Fraction Stereotactic Body Radiotherapy for Localized Prostate Cancer: A Nonrandomized Clinical Trial

Area of Science:

• Oncology
• Radiation Oncology
• Urologic Oncology

Background:

• Stereotactic body radiotherapy (SBRT) is an established treatment for localized prostate cancer, typically delivered in 5 fractions.
• Research is exploring reduced SBRT fractions, but the efficacy and tolerability of single-high-dose SBRT require further investigation.

Purpose of the Study:

• To evaluate the safety and efficacy of single-fraction SBRT in men with localized prostate cancer.
• To assess biochemical disease control and adverse events following a single 19-Gy prostate SBRT dose.

Main Methods:

• A multicenter, single-arm, prospective phase 1/2 clinical trial involving men with low-to-intermediate risk localized prostate cancer.
• Participants received a single 19-Gy fraction of prostate SBRT with urethra-sparing techniques and intrafraction motion control.
• Primary endpoint was 3-year biochemical relapse-free survival (bRFS); secondary endpoints included genitourinary (GU), gastrointestinal (GI), and sexual adverse events (AEs), and quality of life (QOL).

Main Results:

• The 3-year bRFS was 92.9% (95% CI, 85.4%-100%), meeting the primary endpoint.
• Grade 2 GU and GI AEs at 3 years were below 10% and 5%, respectively; one case of grade-3 proctitis occurred.
• Erectile dysfunction (grade ≥2) increased from baseline (21.4%) to 38.4% at 3 years; GU and sexual quality of life scores showed minimal clinically important changes in a subset of patients.

Conclusions:

• Single-fraction 19-Gy urethra-sparing SBRT is a viable treatment option for localized prostate cancer, demonstrating acceptable toxicity and meeting its primary efficacy endpoint.
• The observed 3-year bRFS of 92.9% supports the use of single-fraction SBRT, with low rates of severe GU and GI adverse events.
• Longer follow-up is necessary to fully ascertain long-term disease control and the durability of treatment outcomes.