HDR brachytherapy combined with external beam radiotherapy for unfavorable localized prostate cancer: A single center experience from inception to standard of care.

Purpose: High dose rate (HDR) brachytherapy is increasingly adopted for dose escalation in prostate cancer treatment. We report the clinical efficacy and toxicity of HDR prostate brachytherapy combined with external beam radiotherapy (EBRT) and evaluate the predictability of the biochemical definition of cure of 4-year PSA ≤0.2 ng/mL for failure free survival (FFS).

Methods: A single centre retrospective study was conducted, including all patients with high-tier intermediate risk and high-risk prostate cancer treated with HDR brachytherapy combined with EBRT from 2011 to 2019. Patient and prostate cancer characteristics, treatment, clinical endpoints, and follow up were collected.

Results: Total 319 patients were analyzed. The median age was 68 with median follow up of 77.1 months. Total 142 had high-tier intermediate and 177 had high-risk disease. Brachytherapy doses were initially 20 Gy/2 fractions, and subsequently 15 Gy/1 fraction. All patients received 46 Gy/23 fractions of EBRT. Overall survival at 5 and 9 years was 92.2% and 77.0%, respectively. Failure-free survival (FFS) was 86.0% at 5 years and 76.1% at 9 years. PSA ≤ 0.2 ng/mL at 4 years was seen in 79.3% of patients and was associated with FFS of 94.1% at 9 years. Grade 3 urethral stricture, hematuria, or proctitis occurred in 2.8%, 0%, and 0%, respectively.

Conclusion: HDR brachytherapy in addition to EBRT is effective treatment for unfavourable localized prostate cancer with a very acceptable toxicity profile. The biochemical definition of cure of PSA < 0.2 ng/mL at 4 years was predictive for FFS at 9 years.