A Randomized Controlled Phase 2 Trial Comparing Salvage Radiotherapy for Prostate Cancer Delivered in 4 Versus 2 Weeks (SHORTER): Acute Genitourinary and Gastrointestinal Patient-reported Outcomes at a Single Institution.

BACKGROUND AND OBJECTIVE: Some patients undergoing prostatectomy develop biochemical recurrence or have persistently detectable prostate-specific antigen level. Salvage radiotherapy (RT), delivered over ≥4 wk, is a current standard of care. Our objective was to demonstrate that salvage RT delivered in a five-fraction stereotactic body radiotherapy (SBRT) regimen does not significantly increase patient-reported genitourinary (GU) and gastrointestinal (GI) symptoms compared with a 20-fraction regimen (HYPO).

METHODS: In this randomized noninferiority study, 137 patients were randomized 1:1 to salvage RT with 32.5 Gy in five fractions or 55 Gy in 20 fractions. We report acute changes in Expanded Prostate Cancer Index Composite (EPIC) scores and Common Terminology Criteria for Adverse Events at 3 and 6 mo.

KEY FINDINGS AND LIMITATIONS: The difference in the changes in EPIC GU scores between SBRT and HYPO was 3.3 (95% confidence interval [CI], -8.53, 1.93), indicating a lack of a clinically meaningful difference. The difference in the changes in EPIC GI scores between SBRT and HYPO was 1.16 (95% CI, -5.15, 7.46), indicating a lack of a clinically meaningful difference.

CONCLUSIONS AND CLINICAL IMPLICATIONS: Salvage RT delivered in five fractions was not associated with a significantly worse decline in patient-reported GU or GI toxicities at 3 or 6 mo. Further follow-up is necessary to monitor for potential differences in late toxicity and patient-reported outcomes.