High-dose-rate brachytherapy monotherapy versus low-dose-rate brachytherapy with or without external beam radiotherapy for clinically localized prostate cancer

Background: To compare the outcome of high-dose-rate interstitial brachytherapy (HDR-BT) monotherapy and low-dose-rate brachytherapy (LDR-BT) with or without external beam radiotherapy (EBRT) for localized prostate cancer. Methods and materials: We compared 352 patients treated with HDR-BT as monotherapy (median follow-up time 84 months, NCCN risk classification; low: intermediate: high = 28: 145: 179) and 486 patients with LDR-BT with or without EBRT (90 months, 194: 254: 38). HDR-BT treated advanced disease with more hormonal therapy than LDR-BT. LDR-BT excluded patients with T3b-T4 tumor and initial PSA > 50 ng/ml. Inverse probability of treatment weighting (IPTW) involving propensity scores was used to reduce background selection bias. Results: The actuarial 5-year biochemical failure-free survival rates (bNED) were 92.9% and 95.6% (p = 0.25) in the HDR-BT and LDR-BT groups, respectively, and it was 100% and 97.3% (p = 0.99) in the low-risk, 95.6% and 94.3% (p = 0.19) in the intermediate, 89.6% and 94.9% (p = 0.26) in the high-risk groups, and 93.1% and 94.9% (p = 0.98) in selected high-risk group excluding T3b-4 and initial PSA >= 50. IPTW correction also indicated no difference in bNED between LDR-BT and HDR-BT groups. LDR-BT showed a higher incidence of genitourinary (GU) toxicity grade >= 2 than that of HDR-BT in the acute phase and grade 1 toxicity in late phase. Acute GU toxicity grade >= 1 predicted late GU toxicity grade >= 2. External beam radiotherapy plus LDR-BT elevated GI toxicity than LDR-BT only group. Accumulated incidence of late grade >= 2 GU and GU toxicity was equivalent between HDR-BT and LDR-BT. No grade 4 or 5 toxicities were detected in either modality. Conclusion: HDR-BT monotherapy showed an equivalent outcome to that of LDR-BT with or without EBRT for low-, intermediate-and selected high-risk patients. LDR-BT showed equivalent incidence of grade >= 2 late GI and GU toxicities and higher grade >= 2 acute GU toxicity as that of HDR-BT as a monotherapy. (C) 2018 Elsevier B.V. All rights reserved.