Prognostic influence of parapharyngeal space involvement in nasopharyngeal carcinoma

OBJECTIVE: The study was conducted to evaluate the prognostic influence of parapharyngeal space (PPS) involvement in patients with nasopharyngeal carcinoma. METHODS: Using a semiquantitative method, tumor extension into the parapharyngeal space was graded as: 0: no extension;1: extension not exceed the SO line; and 2:-extension exceed the SO line. Overall survival (OS), relapse-free survival (RFS), freedom from local relapse (FLR), and freedom from distant metastasis survival (FDM) rates were estimated using Kaplan-meier method. Cox regression was also performed to adjust for prognostic factors. RESULTS: The incidence of PPS involvement was 81.8%.Of these patients, 70.1%had grade 1, and 29.9% had grade 2. PPS involvement correlated well with lymphadenopathy (χ2=8.185, P=0.004 0). The 5-year overall survival rates for Grade 0, 1, and 2 extension were 90.2%,75.1%, and 51.2%, respectively (log-rank=16.45, P=0.000 3). The 5-year disease-free survival rates for Grade 0, 1, and 2 extension were 87.2%, 71.5%, and 53.3%, respectively (log-rank=10.87, P=0.004 4). The 5-year freedom from distant metastasis survival rates for Grade 0, 1, and 2 extension were 93.7%, 82.2%, and 62.7%, respectively (log-rank=9.41, P=0.0091). Advanced PPS involvement showed stronger prognostic value than PPS invasion. In multivariate analysis, only advanced PPS involvement had independent predictive value for overall survival, disease-free survival, and freedom from distant metastasis survival rates. CONCLUSIONS: We recommend that the extent of PPS should be clarified and stratified. In view of the prognostic significance, advanced PPS involvement showed stronger predictive value than PPS invasion. Advanced PPS involvement is associated with poorer survival and distant metastasis.