Subcategorization of Perineural Invasion and Its Impact on Survival in Patients with Oral Squamous Cell Carcinoma.

Background: Perineural invasion (PNI) is  recognized as a poor prognostic factor in oral squamous cell carcinoma (OSCC). However, the prognostic significance of further histologic  subcategorization of PNI is inconclusive. In this study, we determined the prognostic relevance of histologic subcategories of PNI and their correlation with the presence of other clinical and pathological parameters METHODS: This is a retrospective study of 207 homogeneously treated OSCC patients with histologically documented PNI from a single center. Univariate and multivariate survival outcomes, namely, local recurrence-free survival (LRFS), disease-free survival (DFS), and overall survival (OS) of patients with various subcategories of PNI,namely- number of foci, size of the involved nerve, extratumoral or intratumoral extent, and intraneural or perineural location-were determined.

Results: Within the histologic subcategories of PNI, tongue primary and presence of lymph node metastasis correlated significantly with the number of nerves involved with PNI. Larger size of involved nerve correlated with advanced tumor stage. Number of foci, extent, and location of PNI were not prognostically significant except size of the involved nerve which showed an inverse correlation with disease outcome as involvement of larger nerves displayed better outcomes in terms of DFS and LRFS but not of OS on multivariate analysis. Addition of adjuvant chemotherapy to radiotherapy emerged as a significant predictor of improved LRFS, DFS, and OS.

Conclusions: Histologic subcategorization of PNI did not have prognostic relevance in our study. Involvement of even small nerves was associated with poor prognosis. Addition of chemoradiation was seen to improve prognosis.