Comparative Effectiveness Of Low-Dose-Rate Brachytherapy Alone Or Combined With External-Beam Radiotherapy In Intermediate-Risk Prostate Cancer: A Propensity-Matched Multi-Institutional Study

We compared clinical outcomes and toxicities associated with seed brachytherapy (SEED-BT) alone and SEED-BT plus external-beam radiotherapy (EBRT) for the treatment of intermediate-risk prostate cancer. From 2006 to 2011, 993 patients diagnosed with intermediate-risk prostate cancer were treated with either SEED-BT alone (n = 775) or SEED-BT plus EBRT (n = 158) at 3 tertiary hospitals. One-to-one propensity score matching was performed to compare clinical outcomes between the groups. In the propensity score-matched analysis (102 pairs), median follow-up was 95 months (range: 18–153 months). The 8-year biochemical recurrence-free rate (bRFR) was significantly better with SEED-BT alone than with combined radiotherapy (93.3% vs. 88.4%; HR: 0.396; 95% CI: 0.158 to 0.991). The cumulative incidence of grade 2 or greater late genitourinary toxicity at 8 years was 21.0% for SEED-BT alone and 33.2% for combined radiotherapy. Grade 2 or greater late genitourinary toxicities were significantly fewer with SEED-BT alone than with combined radiotherapy (HR: 0.521; 95% CI: 0.308 to 0.881). Similarly, grade 2 or greater late gastrointestinal toxicities were significantly fewer with SEED-BT alone (0% vs. 12.2%; HR: 0.125; 95% CI: 0.040 to 0.390). Our study implies that SEED-BT alone might be a better disease-management plan than SEED-BT plus EBRT for intermediate-risk prostate cancer.