High- dose- rate (2 fractions of 13.5 Gy) and low-dose-rate brachytherapy as monotherapy in prostate cancer. Long term outcomes and predictive value of nadir PSA

Abstract

This study aims to evaluate the outcomes of patients treated for low-risk (LR) and favorable intermediate risk (FIR) prostate cancer with brachytherapy (BT) in monotherapy with LDR or HDR and its relationship with nadir PSA (nPSA). We retrospectively analyzed 139 patients (2005-2019) with exclusive LDR (46%. 145/160 Gy) /HDR (54%. 2 implants of 13.5 Gy each separated 10 days). 69% LR and 31% FIR. PSA nadir was grouped into two categories: ≤ 0.2 ng/mL and > 0.2 ng/mL. Median patient age was 69 years (46-84). Seventy-six patients (55%) received androgen deprivation therapy, and 37% received neoadjuvant therapy. Median follow-up period was 90 months. Actuarial biochemical failure-free survival (BFFS), local control (LC), overall survival (OS), and cause-specific survival (CSS) rates for the total cohort were 78%, 87%, 68%, and 98% at 10 years, respectively. BFFS, LC, OS and CSS in nPSA ≤ 0,2 ng/ml was 90%, 96%, 67%, 100% at 10 years respectively, whereas, those with a nPSA > 0.2 ng/ml had a BFFS, LC, OS and CSS of was 37%, 51%, 72%, 90% at 10 years respectively Statistical significance between both groups was reached in BFFS (p=0,000), LC (p=0,000) and CSS (p=0,007)). In the univariate analysis, there was no difference between risk stratification, BT technique, ADT, or the development of bouncing. Prostate brachytherapy as monotherapy (LDR and HDR) is an effective treatment option for patients with LR and FIR prostate cancer. nPSA ≤0,2 ng/ml is a representative value that provides prognostic information for favorable outcomes in this group of patients.