Interfractional anatomical alterations may have a differential effect on the dose delivered by step-and-shoot intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT). The increased degrees of freedom afforded by rotational delivery may increase plan robustness (measured by change in target volume coverage and doses to organs at risk [OARs]). However, this has not been evaluated for head and neck cancer.A total of 10 patients who required repeat computed tomography (CT) simulation and replanning during head and neck IMRT were included. Step-and-shoot IMRT and VMAT plans were generated from the original planning scan. The initial and second CT simulation scans were fused and targets/OAR contours transferred, reviewed, and modified. The plans were applied to the second CT scan and doses recalculated without repeat optimization. Differences between step-and-shoot IMRT and VMAT for change in target volume coverage and doses to OARs between first and second CT scans were compared by Wilcoxon signed rank test.There were clinically relevant dosimetric changes between the first and the second CT scans for both the techniques (reduction in mean D95

作者：David J, Thomson；William J, Beasley；Kate, Garcez；Lip W, Lee；Andrew J, Sykes；Carl G, Rowbottom；Nicholas J, Slevin

来源：Medical dosimetry : official journal of the American Association of Medical Dosimetrists 2016 年 41卷 2期