%0 Journal Article
%T The tumor shape changes of nasopharyngeal cancer during chemoradiotherapy: the estimated margin to cover the geometrical variation
%A Desheng Hu
%A Jianzeng Ye
%A Ruilian Xu
%A Wan He
%A Wenyong Tan
%A Xianming Li
%A Xiaohong Wang
%A Yanping Li
%J SCIE-indexed Journal
%D 2016
%X The introduction of image-guided intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) further improves the precision of radiation delivery (1,2). For head and neck cancer including NPCs, however, considerable geometric changes can occur due to tumor shrinkage and weight loss, water and fat re-distribution, etc., throughout the course of IMRT (3-5). Therefore, additional efforts are needed to optimize the radiation dose delivered to the target volumes (TV) and organs at risk (5-12). In addition, a gradual volumetric loss and the shift of the center of mass of the gross tumor volume (GTV) and clinical target volume (CTV) at several time-points have been quantified with repeated imaging in previous studies (4,5,12). Some studies have demonstrated the necessity of adaptive re-planning at regular fixed intervals (11,13-16). However, the optimal timing (17), algorithms of re-planning (18), and final clinical benefit (16,19) remain unclear. Previous studies have suggested the optimal timing of re-planning was before the 15th (11,16), 20th (6), or 25th (10,14) treatment fraction, with rather arbitrariness. Effective timing of re-planning should depend on the geometrical coverage variations and should be individualized during IMRT (4)
%U http://qims.amegroups.com/article/view/10174/10910