Quantitative Measurement of Perineural Invasion for Prognosis Analysis of Oral Cavity Cancer Treated by Radical Surgery With or Without Adjuvant Therapy

Objectives: Perineural invasion (PNI) was quantitatively analyzed in oral squamous cell carcinoma (OSCC) specimens obtained by radical surgery to correlate with survival outcomes. Methods: This is a retrospective study that reviewed the Cancer registry data between 2009 and 2015. Inclusion criteria were oral cavity cancer, treatment by radical surgery, presence of PNI, and available pathologic samples for S100 staining. Patients with M1 disease and those with synchronous or metachronous cancer during staging work-up were excluded. All pathologic samples were reviewed to confirm PNI status and processed by immunohistochemical staining for S100 to quantify PNI. Pathologic information and staging results were also reviewed, and clinical outcomes were analyzed. Results: The retrospective study included 92 patients; 63 had intratumoral PNI (IPNI) and 29 had extratumoral PNI (EPNI). The average number of PNI foci (APNI) was higher in the EPNI group than in the IPNI group (6.7 vs 3.8, t-test 2-tail significance = 0.021). The 3-year overall survival (OS) and time-to-recurrence (TTR) rates of all patients were 82.5% and 81.2%, respectively. Univariate analysis showed that pathological T4 or N2-3 stage correlated with poor OS, whereas APNI ≥4 correlated with poor TTR. In multivariate analysis, only the pathological N2-3 stage was significantly correlated with poor OS, whereas only APNI ≥ 4 was an independent factor of poor TTR. The 3-year TTR rates were 92.4% and 65.6% for diseases with APNI < 4 and ≥ 4, respectively ( P = .008). Conclusions: In patients with OSCC with PNI, a greater amount of PNI identified by S100 staining indicated a poorer TTR regardless of stage and other prognostic factors. Quantification of PNI by S100 immunohistochemistry is a potential method for prognosis prediction.