title: Should all nasopharyngeal carcinoma with masticator space involvement be staged as T4?
abstract: BACKGROUND
  The prognostic significance of the involvement of anatomical masticator space (MS) in nasopharyngeal carcinoma (NPC) was retrospectively reviewed.
  
  
  METHODS
  1104 Patients with non-metastatic NPC treated with radical radiotherapy between 1998 and 2010 were re-staged according to the 7th edition of the American Joint Committee on Cancer (AJCC) staging system; tumors with medial pterygoid muscle (MP) and/or lateral pterygoid muscle (LP) involvement but did not fulfill the criteria for T3 or T4 were staged as TX. The tumor volume data, dosimetric data and survival endpoints of different T stage diseases were analyzed and compared to study the significance of MS involvement.
  
  
  RESULTS
  The overall MS involvement rate was 61.0%. The median volumes of the primary gross tumor volume were 9.6ml, 15.2ml, 19.9ml, 32.6ml and 77.3ml for T1, T2, TX, T3 and T4, respectively (p<0.001). T1, T2 and TX tumors received higher minimum dose to the gross tumor volume and planning target volume than T3 and T4. Multivariate analysis showed that age, gender, T-/N-classification and the use of chemotherapy were significant prognostic factors for various survival end-points. Patients with TX disease had similar survival rates as with T1-T2; and had a significantly better 5-year overall survival rate (86.6% vs. 76.6%; p=0.013) and a trend of higher 5-year distant failure-free survival rate (91.5% vs. 81.3%; p=0.09) than patients with T3 disease.
  
  
  CONCLUSIONS
  NPC with the involvement of MP and/or LP alone should be classified as T2 disease.
authors.affiliation: Department of Clinical Oncology, Faculty of Medicine, The University of Hong Kong, China. Electronic address: hcksze@hku.hk.
authors.forename: Henry
authors.initials: H
authors.lastname: Sze
authors.affiliation: Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.
authors.forename: Lucy L K
authors.initials: LL
authors.lastname: Chan
authors.affiliation: Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.
authors.forename: W T
authors.initials: WT
authors.lastname: Ng
authors.affiliation: Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.
authors.forename: Albert W M
authors.initials: AW
authors.lastname: Hung
authors.affiliation: Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.
authors.forename: Michael C H
authors.initials: MC
authors.lastname: Lee
authors.affiliation: Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.
authors.forename: Amy T Y
authors.initials: AT
authors.lastname: Chang
authors.affiliation: Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.
authors.forename: Oscar S H
authors.initials: OS
authors.lastname: Chan
authors.affiliation: Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.
authors.forename: F Y
authors.initials: FY
authors.lastname: Cheung
authors.affiliation: Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.
authors.forename: Rebecca M W
authors.initials: RM
authors.lastname: Yeung
authors.affiliation: Clinical Oncology Center, The University of Hong Kong - Shenzhen Hospital, Shenzhen, China.
authors.forename: Anne W M
authors.initials: AW
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008297:Male; D008410:Masticatory Muscles / Q000473:pathology*; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000473:pathology* / Q000532:radiotherapy; D009367:Neoplasm Staging; D011379:Prognosis; D011829:Radiation Dosage; D012189:Retrospective Studies; D047368:Tumor Burden; D055815:Young Adult
keywords: Masticator space; Nasopharyngeal carcinoma; Prognosis; Staging