Zvi Symon1, Jana Menhel, Dror Alezra, M Raphael Pfeffer. 1. Oncology Institute, Sheba Medical Center, Tel Hashomer, affiliated with the Sackler School of Medicine, Tel Aviv University, Israel. symonz@sheba.health.gov.il
Abstract
PURPOSE: To challenge the assumption of unchanged interfractional geometry changes in the course of fractionated multichannel vaginal cuff high-dose-rate brachytherapy. METHODS AND MATERIALS: Two methods of treatment planning for delivery of vaginal cuff brachytherapy were compared in 44 applications. Individual fraction optimization (IFO)-performed for the specific geometry of each individual fraction-was compared to first fraction optimization (FFO)-an optimized first fraction, applied unaltered for geometry of subsequent fractions in the same patient. Dose difference to critical organs was expressed as the percentage of the prescribed dose. RESULTS: In the paired analysis for IFO vs. FFO, mean and maximum rectal and bladder doses were similar. However for FFO, an excess of greater than 20% mean dose to either bladder or rectum was observed in 41% of cases. Maximum organ doses were exceeded by 20% in 54.5% of applications. CONCLUSIONS: On the basis of these findings, it can be concluded that IFO may be important to minimize doses to critical structures.
PURPOSE: To challenge the assumption of unchanged interfractional geometry changes in the course of fractionated multichannel vaginal cuff high-dose-rate brachytherapy. METHODS AND MATERIALS: Two methods of treatment planning for delivery of vaginal cuff brachytherapy were compared in 44 applications. Individual fraction optimization (IFO)-performed for the specific geometry of each individual fraction-was compared to first fraction optimization (FFO)-an optimized first fraction, applied unaltered for geometry of subsequent fractions in the same patient. Dose difference to critical organs was expressed as the percentage of the prescribed dose. RESULTS: In the paired analysis for IFO vs. FFO, mean and maximum rectal and bladder doses were similar. However for FFO, an excess of greater than 20% mean dose to either bladder or rectum was observed in 41% of cases. Maximum organ doses were exceeded by 20% in 54.5% of applications. CONCLUSIONS: On the basis of these findings, it can be concluded that IFO may be important to minimize doses to critical structures.
Authors: Yasir A Bahadur; Camelia Constantinescu; Ashraf H Hassouna; Maha M Eltaher; Noor M Ghassal; Nesreen A Awad Journal: J Contemp Brachytherapy Date: 2014-12-31