Focal low-dose-rate prostate brachytherapy for low- and intermediate-risk prostate cancer

Abstract

Purpose: To prospectively investigate the efficacy and feasibility of focal low-dose-rate (LDR) prostate brachytherapy for low-and intermediate-risk prostate cancer.Material and methods: Between October 2014 and May 2019, nineteen low-and intermediate-risk prostate cancer patients who presented with abnormality on both diffusion-weighted and T2-weighted magnetic resonance imaging (MRI) underwent focal LDR brachytherapy at our institution. Focal gross tumor volume (F-GTV) was delineated on transrectal ultrasound, based on abnormality seen on fused T2-weighted MRI. F-GTV was expanded by 5 mm, as a safety margin, to create focal clinical target volume (F-CTV). Prescribed dose to F-CTV was 145 Gy. Biochemical recurrence (BCR) was determined using Phoenix criterion (prostate specific antigen nadir + 2 ng/ml). Pre-and post-implant dosimetry data were compared using non-parametric Wilcoxon's rank sum test. Treatment-related toxicities were evaluated using common terminology criteria for adverse events.Results: Mean F-CTV D 90% was significantly lower in the post-implant evaluation than in intraoperative planning (p = 0.004). On post-implant dosimetry, the mean D 90% for F-GTV and mean V 100% for the entire prostate were 222 Gy and 35%, respectively. Median follow-up time for all patients was 31 months. BCR occurred in one patient after 23 months. Kaplan-Meier 2-year BCR-free rate was 92.9% (95% confidence interval [CI]: 79.4-100%). No patients had grade 1 or greater gastrointestinal toxicity. Three patients who were taking α-blockers to treat benign prostatic hyperplasia (present before brachytherapy), experienced no treatment-related genitourinary toxicities. Two patients suffered from temporary grade 2 urinary frequency. None of the remaining patients experienced grade 2 or higher genitourinary toxicity.Conclusions: Focal LDR prostate brachytherapy appears acceptable for MRI-based index tumors, with a low cumulative incidence of BCR. Such brachytherapy might offer a feasible minimally invasive therapeutic option for localized prostate cancer.

Focal low dose-rate brachytherapy for low to intermediate risk prostate cancer: preliminary experience at an Australian institution

“…This objective was met in 16 of 17 patients, however, the mean focal GTV size was only 0.7 cc, compared to 3.8 cc in our study. A planning objective of V100% ≥98% to the focal volume has also been used previously (17,19). The post-implant dosimetry and size of the focal target volume reported in our study is comparable to that reported by Cosset et al (15), Mahdavi et al (17) and Kunogi et al (19) (Table 1).…”

“…Despite the increasing uptake of focal therapy for PCa across the globe, including LDR brachytherapy, robust evidence to support its efficacy and optimal utilisation is still maturing and further studies are urgently required (13). Data specifically for lesion-targeted focal LDR brachytherapy is particularly lacking, with only six small studies (total of 115 patients) published to date (Table 1) (14)(15)(16)(17)(18)(19).…”

Efficacy of focal high-dose-rate brachytherapy in the treatment of patients diagnosed with low or favourable intermediate-risk prostate cancer—a protocol for a randomised controlled trial

“…It is a standard treatment method within the framework of clinical trials. The effectiveness and safety of focal LDR BT are well-studied and described in the scientific literature 37 38…”