title: Will weight loss cause significant dosimetric changes of target volumes and organs at risk in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy?
abstract: This study aimed to quantify dosimetric effects of weight loss for nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiation therapy (IMRT). Overall, 25 patients with NPC treated with IMRT were enrolled. We simulated weight loss during IMRT on the computer. Weight loss model was based on the planning computed tomography (CT) images. The original external contour of head and neck was labeled plan 0, and its volume was regarded as pretreatment normal weight. We shrank the external contour with different margins (2, 3, and 5mm) and generated new external contours of head and neck. The volumes of reconstructed external contours were regarded as weight during radiotherapy. After recontouring outlines, the initial treatment plan was mapped to the redefined CT scans with the same beam configurations, yielding new plans. The computer model represented a theoretical proportional weight loss of 3.4% to 13.7% during the course of IMRT. The dose delivered to the planning target volume (PTV) of primary gross tumor volume and clinical target volume significantly increased by 1.9% to 2.9% and 1.8% to 2.9% because of weight loss, respectively. The dose to the PTV of gross tumor volume of lymph nodes fluctuated from -2.0% to 1.0%. The dose to the brain stem and the spinal cord was increased (p < 0.001), whereas the dose to the parotid gland was decreased (p < 0.001). Weight loss may lead to significant dosimetric change during IMRT. Repeated scanning and replanning for patients with NPC with an obvious weight loss may be necessary.
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Tumor Hospital, Fujian Medical University, Fuzhou, China.
authors.forename: Chuanben
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Tumor Hospital, Fujian Medical University, Fuzhou, China.
authors.forename: Zhaodong
authors.initials: Z
authors.lastname: Fei
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Tumor Hospital, Fujian Medical University, Fuzhou, China.
authors.forename: Lisha
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Tumor Hospital, Fujian Medical University, Fuzhou, China.
authors.forename: Penggang
authors.initials: P
authors.lastname: Bai
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Tumor Hospital, Fujian Medical University, Fuzhou, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Lin
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Tumor Hospital, Fujian Medical University, Fuzhou, China. Electronic address: jianjipan@126.com.
authors.forename: Jianji
authors.initials: J
authors.lastname: Pan
mesh_terms: D000328:Adult; D006801:Humans; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000532:radiotherapy*; D058958:Organs at Risk / Q000528:radiation effects*; D011832:Radiation Injuries / Q000209:etiology* / Q000517:prevention & control; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000009:adverse effects* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D047368:Tumor Burden / Q000528:radiation effects; D015431:Weight Loss
keywords: adaptive radiotherapy; dosimetric changes; intensity-modulated radiation therapy; nasopharyngeal carcinoma; weight loss