Prognostic value of grading masticator space involvement in nasopharyngeal carcinoma according to MR imaging findings.
OBJECTIVE
To derive a suitable method for grading masticator space invasion in nasopharyngeal carcinoma on the basis of magnetic resonance (MR) images and to determine its prognostic value in patients undergoing intensity-modulated radiation therapy.


METHODS
After institutional review board approval and informed consent were acquired, 808 patients with nasopharyngeal carcinoma who were treated with definitive intensity-modulated radiation therapy were analyzed retrospectively. The anatomic sites of masticator space involvement were identified with MR imaging. Overall survival, local relapse-free survival, and distant metastasis-free survival were calculated by using the Kaplan-Meier method and were compared by using the log-rank test. Potential prognostic factors were identified by means of multivariate analysis.


RESULTS
Masticator space involvement was diagnosed in 163 of 808 patients (20.2%). Patients with lateral invasion (involvement of the lateral pterygoid muscle of the masticator space and beyond) had significantly poorer overall survival and distant metastasis-free survival than those with medial invasion (involvement of the medial pterygoid muscle of the masticator space) (P = .035 and P = .026, respectively). Furthermore, their overall survival, local relapse-free survival, and distant metastasis-free survival were significantly poorer compared with patients with stage T2 or T3 disease (all P ≤ .023) but similar to patients with stage T4 disease. The grade of masticator space involvement was an independent prognostic factor for overall survival, local relapse-free survival, and distant metastasis-free survival (all P ≤ .023).


CONCLUSIONS
Masticator space involvement in nasopharyngeal carcinoma should be graded as medial (stage T2 disease) or lateral (stage T4 disease). This can facilitate staging of nasopharyngeal carcinoma and may be a suitable prognostic indicator of survival.
From the Cancer Center, Cancer Research Institute, Foshan Hospital, Sun Yat-sen University, Foshan 528000, Guangdong, People's Republic of China (G.Y.Z., X.P.C., T.X., J.W., W.H.W., Z.L.H., M.M.Z., S.T.X., Y.J.W.); and Department of Radiation Oncology (Y.H.), Department of VIP Region (X.Y.C.), and Imaging Diagnosis and Interventional Center (L.Z.L.), State Key Laboratory of Oncology in Southern China, Cancer Center, Sun Yat-sen University, Guangzhou, Guangdong, People's Republic of China.
Guo-Yi
GY
Zhang
Ying
Y
Huang
Xiu-Yu
XY
Cai
Xiang-Ping
XP
Chen
Tao
T
Xu
Jing
J
Wu
Wei-Hong
WH
Wei
Li-Zhi
LZ
Liu
Ze-Li
ZL
Huang
Miao-Miao
MM
Zhou
Shi-Tong
ST
Xia
Yue-Jian
YJ
Wang
D000293:Adolescent; D000328:Adult; D000368:Aged; D002277:Carcinoma; D003131:Combined Modality Therapy; D003952:Diagnostic Imaging; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D060787:Neoplasm Grading; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D009367:Neoplasm Staging; D011379:Prognosis; D011626:Pterygoid Muscles / Q000473:pathology; D050397:Radiotherapy, Intensity-Modulated; D012189:Retrospective Studies