Predictive factors of long-term rectal toxicity following permanent iodine-125 prostate brachytherapy with or without supplemental external?beam radiation therapy in 2216 patients

摘要

PurposeWe analyzed factors associated with rectal toxicity after iodine-125 prostate brachytherapy (BT) with or without external beam radiation therapy (EBRT). Methods and MaterialsIn total, 2216 prostate cancer patients underwent iodine-125 BT with or without EBRT between 2003 and 2013. The median followup was 6.9?years. Cox proportional hazards modeling was used for univariate and multivariate analyses to assess clinical and dosimetric factors associated with rectal toxicity. Dosimetric parameters from 1?day after implantation (Day 1) and 1?month after implantation (Day 30) were included in the analyses. ResultsThe 7-year cumulative incidence of Grade 2 or higher rectal toxicity was 5.7% in all patients. The multivariate analysis revealed that antiplatelet or anticoagulant therapy, neoadjuvant androgen deprivation therapy, treatment modality, Day 1 rectal volume receiving 100% of the prescribed dose (RV100), and the Day 30 minimal percent of the prescribed dose delivered to 30% of the rectum (RD30) were associated with rectal toxicity. Day 1RV100was a common predictor in both BT-alone and the BT?+?EBRT groups. The 5-year cumulative incidence of Grade 2 or higher rectal toxicity was 12.6%, 5.9%, and 1.7% for BT?+ 3-dimensional conformal radiation therapy, BT?+?intensity-modulated radiation therapy, and the BT-alone groups, respectively (p?