Toxicity and Clinical Outcomes of Single-Fraction High-Dose-rate Brachytherapy Combined with External Beam Radiotherapy for High-/Very High-Risk Prostate Cancer: A Dosimetric Analysis of Toxicity

Purpose The purpose of this study was to investigate the clinical outcomes, urinary function, quality of life (QOL), and toxicities in high- or very high-risk prostate cancer patients undergoing single-fraction high-dose-rate brachytherapy (HDR-BT) with external beam radiotherapy (EBRT) and analyze the relationship between dosimetric parameters and toxicities. Materials and methods Between April 2014 and April 2019, 124 patients underwent 13-Gy HDR-BT followed by EBRT (46 Gy/23 fractions). Urinary function and QOL were evaluated using IPSS and 7-grade QOL Scale, respectively. Biochemical progression-free survival (bPFS) was calculated. Results Median follow-up period was 35.8 months; all patients received neoadjuvant hormonal therapy and very high-risk patients received adjuvant hormonal therapy. Only one patient developed a grade 3 toxicity (hematuria). Multivariate analysis showed the dose covering 30% of the urethral volume, bladder volume receiving 75% of the dose, and dose covering 2 cc of rectum were independent predictors of acute G2 urinary frequency, acute G2 urinary retention, and late G2 rectal hemorrhage. IPSS and QOL scores significantly increased following HDR-BT and returned to baseline within 6 months. The 2-year bPFS was 99.2%. Conclusion The single-fraction HDR-BT with EBRT is a safe treatment for quicker recovery of urinary symptoms and QOL. The dose of at-risk organs correlated with toxicities. Secondary abstract Single-fraction high-dose-rate brachytherapy (HDR-BT) combined with external beam radiotherapy (EBRT) for prostate cancer is a safe treatment allowing for quicker recovery of urinary symptoms and QOL. The dose of at-risk organs correlated with toxicities.