The effectiveness of high-dose-rate brachytherapy with external beam radiotherapy for clinically locally advanced and node-positive prostate cancer: long-term results of a retrospective study.

Background: No standard treatment exists for locally advanced prostate cancer (PC). This study evaluated the long-term treatment outcomes and toxicity in patients with clinically locally advanced and/or lymph node (LN)-positive PC who underwent high-dose-rate brachytherapy (HDR-BT) with external beam radiotherapy (EBRT).
Methods: The treatment outcomes and toxicities of 152 patients with PC who underwent HDR-BT with EBRT and had at least 2 years of observation were examined. The treatment dose was 19- and 13-Gy HDR-BT in two and single fractions, respectively, both combined with external irradiation of 46 Gy in 23 fractions. Long-term androgen deprivation therapy (ADT) for patients harboring very high-risk tumors was used in combination.
Results: The median observation period was 59.7 (24.4-182.1) months. The 5-year prostate cancer-specific and recurrence-free (RFS) survival rates were 99.0% and 91.8%, respectively, with only two PC mortalities. When 5-year RFS was examined for each parameter, RFS was significantly lower in pre-radiotherapy (pre-RT) prostate-specific antigen (PSA) > 0.5 ng/mL (77.1%; p = 0.008), and presence of LN metastasis (68.1%; p = 0.017). Multivariable analysis demonstrated that pre-RT PSA (HR, 4.68; 95% CI, 1.39-15.67; p = 0.012) and presence of LN metastasis (HR, 4.70; 95% CI, 1.24-17.74; p = 0.022) were independent recurrence predictors. The 5-year cumulative incidence rate of grade ≥ 2 toxicities in genitourinary and gastrointestinal tracts were 15.4% and 1.3%, respectively.
Conclusions: HDR-BT combined with EBRT and long-term ADT shows promising disease control and tolerant toxicities for clinically locally advanced and LN-positive PC.
(© 2021. Japan Society of Clinical Oncology.)