Long-Term Outcome and Late Toxicity Analysis for Clinically Localized Prostate Cancer Treated With Permanent Interstitial Brachytherapy

rectum V50) were obtained corresponding to each image data set and the difference was recorded. Results: There were statistically significant differences in all DVH parameters between the 2 image data sets, with the exception of the V100. Excluding one patient in whom there was an 11% decrease in the V100 from 99.5 to 88.5 with and without stylets, the median decrease in prostate V100 was not significant. However, there was a 3.4% decrease for the V125 (p ! 0.001). For urethra V100, the difference was impressive with a mean of 6 and standard deviation (SD) of 12 between the 2 data sets (p ! 0.001). A similar large discrepancy was found for rectum V50 with a mean of 7 and SD of 11.9 (p! 0.001). Conclusions:Significant differenceswerenoted in terms ofDVHparameters between image data sets acquired with and without rigid stylets for the purpose of real-time intraoperative HDR planning for prostate BT. While the difference in terms of prostate coverage may not be clinically relevant, there were large variations in urethral and rectal dosimetry that may result in increased treatment-related toxicity. When using Flexiguide catheters for HDR prostate BT, we recommend performing the intraoperative planning based on an image set with the rigid stylets removed.