Prognostic value of paranasopharyngeal extension of nasopharyngeal carcinoma: A significant factor in local control and distant metastasis

Abstract

BACKGROUND. This study was conducted to evaluate the prognostic value of paranasopharyngeal extension in local control and distant metastasis in patients with nasopharyngeal carcinoma. METHODS. Three hundred and sixty- four patients with newly diagnosed nasopharyngeal carcinoma without distant metastasis were reviewed. Patients were staged according to Ho's staging system. Using a semiquantitative method, tumor extension into the paranasopharyngeal space was graded as: 0: no extension; 1:-extension to the retrostyloid space; 2:-extension to the prestyloid space; and 3:-extension to the anterior part of the masticator space. All patients received radiotherapy as primary treatment. Median follow-up time was 45 months (range, 4.7 to 76.5 months). Relapse free, local relapse free, and distant metastasis free survival were estimated using the Kaplan-Meier method. Cox regression was also performed to adjust for prognostic factors. RESULTS. The incidence of paranasopharyngeal extension was high (72.5%). Of these patients, 65.5% had Grade 2 or 3 extension. The 5-year relapse free survival rates for Grade 0, 1, 2, and 3 extension were 76%, 70%, 46%, and 43%, respectively. The main difference was between Grade 0/1 and Grade 2/3 extension, the latter having a lower 5-year local control rate (86% in Grade 0/1 vs. 72% in Grade 2/3: P < 0.0001) and distant metastasis free survival rate (87% in Grade 0/1 vs. 68% in Grade 2/3; P = 0.0002). Multivariate analysis showed that Grade 2/3 paranasopharyngeal extension was an independent factor in predicting overall relapse, local relapse, and distant metastasis. Advanced T classification (T3) was another independent factor in predicting overall and local relapse, whereas advanced N classification (N3) was another independent factor in predicting overall relapse and distant metastasis. CONCLUSIONS. Extensive paranasopharyngeal extension (Grade 2/3) was an independent prognostic factor associated with poorer treatment outcome, both in local control and distant metastasis. Ho's T2 disease should be further subclassified into T2a and T2b, which include Grade 0/1 and Grade 2/3 paranasopharyngeal disease, respectively.