title: Prognostic value of MRI-derived masticator space involvement in IMRT-treated nasopharyngeal carcinoma patients.
abstract: OBJECTIVE
  This retrospective study reassessed nasopharyngeal carcinoma (NPC) patients treated with intensity-modulated radiation therapy (IMRT), to determine the significance how magnetic resonance imaging (MRI)-derived masticator space involvement (MSI) affected patients' prognosis.
  
  
  METHODS
  One thousand one hundred ninety seven NPC patients who had complete set of MRI and medical records were enrolled. Basing on their MRI findings, the T-categories of tumors were identified according to the seventh edition of American Joint Committee on Cancer staging system, which considers MSI a prognostic indicator for NPCs. Rates of overall survival (OS), local relapse-free survival (LRFS), regional relapse-free survival (RRFS) and distant metastasis-free survival (DMFS) were analyzed by the Kaplan-Meier method, and the Log-Rank test compared their differences. Cox regression analysis was employed to evaluate various prognostic factors systematically. Statistical analyses were conducted with SPSS 18.0 software, P value < 0.05 was considered statistically significant.
  
  
  RESULTS
  Medial pterygoid muscle (MPM) was involved in 283 (23.64 %) cases, of which lateral pterygoid muscle (LPM) was concurrently affected in 181 (15.12 %) and infratemporal fossa (ITF) in 19 (1.59 %). Generally, MSI correlated with an OS, LRFS, and DMFS consistent with a T4-stage diagnosis (P > 0.05). Although different degrees of MSI presented a similar OS and DMFS (P > 0.1), tumors involving LPM had a relatively poorer LRFS than those affected the MPM only (P = 0.027), even for subgroup of patients composed of T3 and T4 classifications (P = 0.035). A tumor involving MPM brought an LRFS consistent with a T2 or T3-stage disease (P > 0.1). If the tumor affected LPM or ITF concurrently, the survival outcomes were more consistent with a T4-stage disease (P > 0.1). Nevertheless, compared to tumor infiltrating MPM, those invading LPM or ITF more frequently spread into other concurrent sites that earned higher T-staging categories. Moreover, multivariate analyses indicated the degree of MSI was a significant prognostic factor for the OS of NPCs (P = 0.036).
  
  
  CONCLUSIONS
  Degree of MSI is a significant prognosticator for the OS of IMRT-treated NPCs, and the prognosis of patients with lateral MSI extension (LPM and ITF) were shown to be significantly worse than those affected only MPM or the T3-stage disease. Thus, it is highly recommended that lateral MSI extension be a higher T-staging category.
authors.affiliation: Department of Radiology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. xyp999@yeah.net.|Provincial Clinical College of Fujian Medical University, No. 1, Xueyuan Road, Fuzhou, 350014, Fujian Province, P. R. China. xyp999@yeah.net.
authors.forename: Youping
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. panjianji@126.com.|Provincial Clinical College of Fujian Medical University, No. 1, Xueyuan Road, Fuzhou, 350014, Fujian Province, P. R. China. panjianji@126.com.
authors.forename: Jianji
authors.initials: J
authors.lastname: Pan
authors.affiliation: Department of Radiology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. yunbinchen@126.com.|Provincial Clinical College of Fujian Medical University, No. 1, Xueyuan Road, Fuzhou, 350014, Fujian Province, P. R. China. yunbinchen@126.com.
authors.forename: Yunbin
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. linshaojun@yeah.net.
authors.forename: Shaojun
authors.initials: S
authors.lastname: Lin
authors.affiliation: Department of Radiology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. cheyne09@163.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. zongjingfeng@126.com.|Provincial Clinical College of Fujian Medical University, No. 1, Xueyuan Road, Fuzhou, 350014, Fujian Province, P. R. China. zongjingfeng@126.com.
authors.forename: Jingfeng
authors.initials: J
authors.lastname: Zong
authors.affiliation: Department of Radiology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. fangyanhong1981@sina.com.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. guoqiaojuan@163.com.|Provincial Clinical College of Fujian Medical University, No. 1, Xueyuan Road, Fuzhou, 350014, Fujian Province, P. R. China. guoqiaojuan@163.com.
authors.forename: Qiaojuan
authors.initials: Q
authors.lastname: Guo
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. chenbj1208@foxmail.com.|Provincial Clinical College of Fujian Medical University, No. 1, Xueyuan Road, Fuzhou, 350014, Fujian Province, P. R. China. chenbj1208@foxmail.com.
authors.forename: Bijuan
authors.initials: B
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Fujian Provincial Cancer Hospital & Institute, No. 420, Fuma Road, Fuzhou, 350014, Fujian Province, P. R. China. tanglinbocn_cn@163.com.|Provincial Clinical College of Fujian Medical University, No. 1, Xueyuan Road, Fuzhou, 350014, Fujian Province, P. R. China. tanglinbocn_cn@163.com.
authors.forename: Linbo
authors.initials: L
authors.lastname: Tang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma; D002648:Child; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000401:mortality / Q000473:pathology* / Q000532:radiotherapy*; D009367:Neoplasm Staging / Q000379:methods*; D011379:Prognosis; D016016:Proportional Hazards Models; D050397:Radiotherapy, Intensity-Modulated; D012189:Retrospective Studies; D055815:Young Adult