Safety and early outcomes of external beam radiation therapy with low dose brachytherapy boost in patients with prostate cancer: A single institution experience.

Purpose: To evaluate the safety and early oncologic outcomes of external beam radiation therapy (EBRT) combined with a low-dose-rate (LDR) brachytherapy boost in patients with intermediate- and high-risk prostate cancer, as contemporary real-world evidence remains limited.

Methods and materials: Investigators retrospectively reviewed 307 patients treated at a large tertiary cancer center between 1999 and 2024. Median age was 66 years; 36% had intermediate-risk and 64% had high- or very high-risk disease, and 91% received androgen deprivation therapy. Late gastrointestinal (GI) and genitourinary (GU) toxicities were defined as occurring more than three months after radiation initiation and graded using CTCAE version 5. Biochemical failure was defined using Phoenix criteria. Outcomes were summarized descriptively; Cox regression analyzed overall survival (OS) and biochemical recurrence-free survival (bRFS), while Fine-Gray models evaluated late toxicity with death as a competing risk.

Results: At a median follow-up of 4.6 years, 22 patients developed biochemical recurrence. Five-year bRFS was 98% for intermediate-risk disease and 90% for high- or very high-risk disease; OS and bRFS were 92% and 95%, respectively. Grade 3 or higher GU and GI toxicity occurred in 3.2%, and no significant predictors of severe late toxicity were identified.

Conclusion: These findings support this approach for appropriately selected patients in routine clinical care.