Standardized treatment planning for high dose rate vaginal cuff brachytherapy

摘要

AbstractThe purpose of this study was to establish the efficacy of standardized treatment planning for high dose rate (HDR) vaginal cuff brachytherapy in order to simplify and shorten the brachytherapy procedure. Two separate but related studies are presented. The first examined the reproducibility of treatment planning by assessing interoperator variability. This provided a baseline assessment of variability to evaluate standardized treatment planning in the second study. The second study examined interpatient variability in which the treatment plans of 20 patients were investigated by two different treatment methods. The first method used the dosimetry of the first insertion for the next insertion, while the other method utilized a standardized plan for all insertions dependent upon ovoid size. The dose was prescribed to the vaginal surface using either applicator points or dose points. Based on multiple calculations, a graph of distance vs. dose was generated to determine the dose to the bladder and rectum for a given implant. In the first study, interoperator variability was acceptable with a standard deviation of 0.4 of the prescribed dose using dose points for the worst case. Applicator points were less reproducible with a worst‐case standard deviation of 2.1 of the prescribed dose. In the second study, implementing initial dosimetric plans for the second implant for an individual patient yielded a worst‐case standard deviation of 2.4 of the prescribed dose. The use of standardized treatment plans for all implants was also efficacious with a worst‐case standard deviation of 1.7 of the prescribed dose. Treatment plans were always more reproducible when calculated to dose points rather than applicator points. Analysis of maximum bladder and rectal doses provided acceptable late tissue doses as predicted by the linear quadratic model. In conclusion, standardized dosimetry plans for vaginal cuff insertion are feasible and reliable in producing precise delivery of vaginal surface doses. The use of dose vs. distance curves facilitates rapid planning by providing a close approximation of the maximum bladder and rectal doses. © 1995 Wiley‐L