Early outcomes after focal high-dose-rate brachytherapy in low- and favorable intermediate-risk prostate cancer: promising early results from a prospective randomized trial.

Objectives: To compare the QoL of patients diagnosed with low- or favorable-intermediate-risk PCa after focal HDR brachytherapy and active surveillance. Our secondary objectives were to compare progression-free survival (PFS) between patients who underwent focal treatment and those who were actively surveilled and to assess early and late GU and GI adverse effects after the focal HDR brachytherapy. Methods: This prospective randomized controlled trial was conducted at the National Cancer Center located in Vilnius, Lithuania. The study was initiated after approval from the Vilnius Regional Biomedical Research Ethics Committee was obtained (Approval ID 2022/6-1438-911). Twenty-seven patients were assigned to the AS group and 28 to the focal HDR group. Results: During the median follow-up time of 14 and 17 months for AS and HDR groups, respectively, the QoL, evaluated by the EORTC QLQ-30 and PR25 instruments, showed no statistically significant differences in functional scores between the groups after baseline adjustment. Additionally, patients in the HDR group reported better urinary outcomes as measured by EORTC PR25 and IPSS scores at 6, 12, and 18 months. There were no statistically significant differences in erectile function between the groups as measured by the IIEF. Early toxicity was low (no Grade ≥3 events), and only two cases (7.1 %) of Grade 2 GU toxicity were reported in the HDR group within the first 3 months, with one case persisting for 6 months. Late toxicity was not assessed during this interim follow-up. The HDR group demonstrated a non-significant trend toward better oncological outcomes, with fewer PSA-based recurrences and a higher mean PFS than the AS. At the time of last follow-up, 49/55 (89 %) patients were censored (22/27 in the AS and 27/28 in the HDR group). Conclusions: A current study shows comparable QoL and early toxicity results between AS and HDR groups. Any domain-level signals were below MCID and did not persist after baseline adjustment. Results of PFS are underpowered at this interim analysis due to short follow-up and high censoring, and should be considered hypothesis-generating only. However, as current results are only exploratory and insufficient to assess durable disease control or late toxicity, a longer follow-up, larger cohorts, and a multicenter approach are needed to provide definitive outcomes to demonstrate the benefit of focal brachytherapy.