Treatment Results of High-dose- rate Brachytherapy and External Beam Radiation With Long-term Androgen Deprivation Therapy for Patients With Metastatic Prostate Cancer

Background/Aim: A recent clinical trial indicated the usefulness of local radiation therapy of the prostate in patients with low-volume metastatic prostate cancer. High-dose-rate brachytherapy (HDR-BT) is used mainly for high-risk, localized, and locally advanced cases. However, few studies exist on the efficacy of HDR-BT and external beam radiation therapy (EBRT) for metastatic prostate cancer. Patients and Methods: We conducted a retrospective analysis of 39 patients diagnosed with regional lymph node metastasis and/or a limited number of metastases who underwent HDR-BT and EBRT with long-term androgen deprivation therapy. We utilized Cox's proportional hazards models to identify predictors of oncological outcomes. Treatment outcomes, including biochemical recurrence-free survival (BCRFS), clinical progression-free survival (CPFS), and castration-resistant prostate cancer-free survival (CRPCFS), were compared according to the clinical stage. Results: The median follow-up duration was 49 months (range=23-136 months). The 5-year BCRFS, CPFS, CRPCFS, and cancer-specific survival rates were 62.2%, 67.2%, 83.2%, and 93.4%, respectively. Based on Kaplan-Meier analysis, N1M0 and N0-1M1b showed favorable outcomes compared with N1M1a. Multivariate analysis revealed that N1M1a prostate cancer was an independent risk factor for poor BCRFS, CPFS, and CRPCFS. Conclusion: HDR-BT and EBRT with androgen deprivation therapy is a feasible approach for patients with newly diagnosed regional and low-metastatic-burden prostate cancer. However, in our cohort M1a prostate cancer had significantly inferior outcomes. A well-controlled prospective study is imperative to confirm our results.