Pterygomandibular raphe invasion as a prognostic factor in squamous cell carcinoma of the buccal mucosa

Abstract

This retrospective study assessed the prognostic significance of pterygomandibular raphe (PMR) invasion in resectable squamous cell carcinoma of the buccal mucosa (SCCBM). We included 82 patients with SCCBM who underwent radical resection at Kumamoto University Hospital between 2000 and 2017. Patients were categorized into three groups based on PMR invasion patterns: noncontact, contact, and invasion. The relationship between PMR invasion and clinicopathological characteristics was analyzed using Fisher’s exact test. The Kaplan–Meier method, log-rank test, and Cox regression model were employed for survival analysis. Results indicated that contact or invasion into the PMR was significantly associated with advanced clinical T and N stages, clinical stage, endophytic growth pattern, high-grade invasion pattern, poor tumor differentiation, extranodal extension, and distant metastasis. Patients with PMR invasion experienced a significantly higher proportion of recurrences in the buccal, subcutaneous, mandibular, and masticatory spaces. Univariate analysis indicated that PMR invasion by contact or invasion type SCCBM was a predictor for worse local control rate, disease-free survival, and overall survival, while multivariate analysis revealed that it was an independent worse prognostic factor for overall survival. Thus, PMR invasion is a key prognostic factor in resectable SCCBM.