Comparing organ-at-risk doses for high–dose rate vaginal brachytherapy between three different planning workflows

Publication date: Available online 28 December 2016
Source:Brachytherapy
Author(s): J.D. Gruhl, D. Zheng, J.L. Longo, C. Enke, A.O. Wahl
PurposeThe aim of this study was to compare the organ-at-risk doses to the rectum and the bladder in postoperative endometrial cancer patients who receive high–dose rate vaginal brachytherapy (HDR-VB), when using three different methods of treatment planning: (Workflow A) individualized treatment planning before every fraction, (Workflow B) individualized treatment planning for first fraction only), and (Workflow C) using a template plan based on applicator choice and prescription specifics without patient-specific imaging or planning (standardized template approach).Methods and MaterialsAlternative plans were retrospectively created using workflows B and C for 22 patients who previously received postoperative HDR-VB using a vaginal cylinder and planned using Workflow A for endometrial cancer. The rectum and bladder were contoured on the CTs used for each fraction for dose comparison between the three methods. D50, D2cc, D1cc, D0.1cc, and V100 of the bladder and the rectum were compared using the two-sided Wilcoxon signed-rank test.ResultsA total of 123 fractions were available for comparison. For Workflow A vs. Workflow B, there was no significant difference for any rectal or bladder dosimetric parameter. For Workflow A vs. Workflow C, Workflow A delivered a significantly higher median dose to the rectum than Workflow C for D50, D2cc, D1cc, and V100. Workflow C delivered a significantly higher dose to the bladder than Workflow A: D2cc, D1cc, D0.1cc, and V100. However, the magnitudes of the differences were small; the dose index difference was >75 cGy for only two fractions.ConclusionPlan standardization in HDR-VB may result in considerable time and cost savings with minimal organ-at-risk dose differences.



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