Effect of Adequate Local Radiation Dose on Oncological Outcomes in Localized Prostate Cancer Patients Treated With Low-dose-rate Brachytherapy

Background/Aim: We retrospectively investigated the effect of a biologically effective dose (BED) of Low-dose rate brachytherapy (LDR-BT) and its possible interaction with androgen deprivation therapy (ADT) during LDR-BT treatment for intermediate-risk prostate cancer ( PCa). Patients and Methods: A total of 693 patients with localized, intermediate-risk PCa, who underwent LDR-BT with or without supplemental external beam radiotherapy, were included in this study. We stratified patients into two groups according to BED (<180 Gy2, lower BED group; >= 180 Gy2, higher BED group) and evaluated the effect of ADT duration on the oncological outcomes of each group. Results: In total, 431 patients received BED >= 180 Gy2. Significant differences in biochemical recurrence-free survival (BCRFS) and clinical progression-free survival ( CPFS) were observed among the non-ADT, ADT <= 3 months, and ADT >3 months subgroups of the lower BED group (p=0.005 and 0.049, respectively). However, no significant differences in BCRFS or CPFS were detected in the higher BED group (p=0.63 and 0.76, respectively). Multivariate analysis of BCR and CP in the lower BED group revealed a significant decreasing trend in the BCRFS (p for trend=0.001) and CPFS rates (p for trend=0.015) as ADT duration increased, which was associated with favorable outcomes. However, no significant trend was observed in the BCRFS or CPFS rate in the higher BED group. Conclusion: An adequate local radiation dose provides favorable oncological outcomes and could potentially reduce the need for long-term ADT.