title: The Impact of Clinical Stage on Radiation Doses to Organs at Risk Following Intensity-modulated Radiotherapy in Nasopharyngeal Carcinoma: A Prospective Analysis.
abstract: Background:The development of intensity-modulated radiotherapy (IMRT) has revolutionized the management of nasopharyngeal carcinoma (NPC). The purpose of this study was to investigate the impact of clinical stage on radiation doses to organs at risk (OARs) in NPC.Material and Methods:One hundred and forty-eight patients with newly diagnosed and untreated NPC were prospectively enrolled. Based on the anatomic definition and pathogenesis of radiation induced injury, a total of 28 OARs surrounding the nasopharynx were contoured on axial computed tomography (CT) planning images in each patient. Dose-volume histograms, as well as the mean and maximal doses for each structure, were calculated.Results:Radiation doses to 15 OARs (including the brain stem, temporal lobe and eye) were positively correlated with T stage, the radiation doses to 13 OARs (including the brachial plexus, parotid and thyroid) increased significantly with N stage, and the radiation doses to the spinal cord and mandible had no association with T or N stage. Based on the characteristic of excess rates, 9 OARs (e.g. spinal cord, eye, trachea, andet al.) met tolerance doses easily in all stages, 9 OARs (e.g. brain stem, temporal lobe, brachial plexus, andet al.) easily in early stages but with difficulty in advanced stages, and 10 OARs (e.g. cochlea, parotid, thyroid, andet al.) with difficulty in all stages.Conclusions:The radiation doses to most of OARs are associated with T or N stage, and there are three kinds of patterns for them: 1) meet tolerance doses easily in all stages; 2) meet tolerance doses easily in early stages but with difficulty in advanced stages; and 3) meet tolerance doses with difficulty in all stages.
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, Guangdong Province, People's Republic of China;; Department of Oncology, Guangzhou First People's Hospital, Guangzhou Medical University, 1 Panfu Road, Guangzhou 510180, Guangdong Province, People's Republic of China.
authors.forename: Lin
authors.initials: L
authors.lastname: Xu
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, Guangdong Province, People's Republic of China;; Department of Radiation Oncology, the Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai 519001, Guangdong Province, China.
authors.forename: Ji-Jin
authors.initials: JJ
authors.lastname: Yao
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, Guangdong Province, People's Republic of China.
authors.forename: Guan-Qun
authors.initials: GQ
authors.lastname: Zhou
authors.affiliation: Department of Medical Statistics and Epidemiology & Health Information Research Center & Guangdong Key Laboratory of Medicine, School of Public Health, Sun Yat-sen University, Guangzhou 510080, Guangdong Province, China.
authors.forename: Wang-Jian
authors.initials: WJ
authors.lastname: Zhang
authors.affiliation: Department of Oncology, Guangzhou First People's Hospital, Guangzhou Medical University, 1 Panfu Road, Guangzhou 510180, Guangdong Province, People's Republic of China.
authors.forename: Guo-Long
authors.initials: GL
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Imaging Diagnosis and Interventional Center, Sun Yat-sen University Cancer Center, Guangzhou 510060, People's Republic of China.
authors.forename: Li-Zhi
authors.initials: LZ
authors.lastname: Liu
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, Guangdong Province, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, Guangdong Province, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Sun
keywords: Clinical stage.; Excess rate; Nasopharyngeal carcinoma; Organs at risk; Radiation doses