Dosimetric comparison between treatment plans of patients treated with low-dose-rate vs. high-dose-rate interstitial prostate brachytherapy as monotherapy: Initial findings of a randomized clinical trial

Abstract

PurposeThe aim of this study was to compare the dosimetry of intraoperative dose plans of prostate cancer patients treated with low-dose–rate (LDR) and high-dose–rate (HDR) interstitial brachytherapy (BT). Methods and MaterialsA randomized clinical trial was initiated at our institution to compare the results and side effects of LDR and HDR BT as monotherapy in the treatment of early, organ-confined prostate cancer patients. Eighty-seven patients were randomly assigned to receive HDR afterloading BT with one fraction of 19 Gy or permanent LDR 125I seed BT with 145 Gy. Inverse optimization algorithms were used for planning. Stranded seeds were implanted using live ultrasound imaging after preimplant treatment planning. Final dosimetry of HDR treatments was based on updated needle and contour positions. Statistical comparisons with nonparametric test were performed between the corresponding dose–volume parameters. ResultsThe V100 and V150 were 99% and 61%, respectively, for LDR, whereas 98% and 32% for HDR treatments. The D90 was less for HDR (122% vs. 110%). The dose distributions were more homogeneous and conformal with HDR technique (dose homogeneity index, 0.39 vs. 0.67; conformal index, 0.65 vs. 0.80). The urethra and rectum received significantly less dose with HDR. The D10 and D30 for urethra were 133% and 128%, respectively, for LDR and 114% and 111% for HDR treatments. The D2cm3 for rectum was 68% and 55% for LDR and HDR technique, respectively. ConclusionsBoth techniques provided acceptable target volume coverage with a slightly higher value with the LDR technique. The dose distributions were more homogeneous and conformal, and both urethra and rectum were better protected with the HDR technique.