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

Abstract

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). 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. 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. An adequate local radiation dose provides favorable oncological outcomes and could potentially reduce the need for long-term ADT.