Multicenter Evaluation of Biochemical Relapse-Free Survival Outcomes for Intraoperatively Planned Prostate Brachytherapy Using an Automated Delivery System.

Abstract

To report biochemical recurrence in prostate cancer treated with intraoperatively planned low-dose-rate prostate brachytherapy using an automated delivery system (IO-LDRB). Between 2003 and 2013, 2608 patients from 3 centers were treated with IO-LDRB as single-modality treatment for low or low-tier intermediate-risk prostate cancer. Databases from the 3 centers have been analyzed. These independent databases were collected prospectively. Patient, tumor, and treatment characteristics were then compared, Kaplan-Meier survival estimates of biochemical relapse-free survival (bRFS) were generated, and the Cox proportional hazards model was used to determine factors predicting for relapse. A total of 2608 patients with a median follow-up of 4.7 (interquartile range, 3.1-6.9) years were analyzed. Median age was 64 (range, 42-84) years. In these patients, median initial prostate-specific antigen was 5.5 ng/mL, 74% were T1, and 26% were T2; 73% were Gleason 6, and 25% Gleason 7. Median percentage of biopsy cores positive was 33%, and median gland volume was 34.2 cm³. Eleven percent of patients received hormones for a median of 3.0 months before implantation. Median seed activity was 0.437 mCi, D90 (dose covering 90% of the prostate volume) was 186.7 Gy, and V100 was 99.37%. Biochemical relapse was observed in 124 patients (4.8%), and median time to failure was 4.0 years. Predicted bRFS was 93% at 7 years. On Cox regression bRFS was dependent only on D90 at the time of implantation and prostate-specific antigen density. This study demonstrates that IO-LDRB is an effective treatment option for patients with low and low-tier intermediate-risk prostate cancer. Rates of biochemical relapse remain low several years after treatment. These results compared favorably to published manual preplan technique results.