Prognostic impact of extratumoral perineural invasion in patients with oral cavity squamous cell carcinoma

PURPOSE: Perineural invasion (PNI) is an adverse prognostic factor in patients with oral cavity squamous cell carcinoma (OCSCC). The American Joint Committee on Cancer Staging Manual, eighth edition, introduced a subdivision of PNI into two distinct forms, that is, extratumoral and intratumoral PNI (EPNI and IPNI, respectively). We designed the current study to assess whether EPNI and IPNI have different prognostic implications in terms of disease control and survival outcomes in patients with OCSCC. MATERIALS AND METHODS: We retrospectively examined 229 consecutive patients with OCSCC and PNI who underwent radical surgery between July 2003 and November 2016. EPNI and IPNI were identified in 76 and 153 patients, respectively. The 5‐year locoregional control (LRC), distant metastasis, disease‐free survival (DFS), and overall survival (OS) rates served as the main outcome measures. RESULTS: Compared with patients showing IPNI, those with EPNI had a higher prevalence of worst pattern of invasion type‐5 (P < 0.001), alcohol consumption (P = 0.03), and close margins (P = 0.002). Univariate analysis revealed that EPNI was a significant predictor of 5‐year LRC (P = 0.024), DFS (P = 0.007), and OS (P = 0.034) rates. After allowance for potential confounders in multivariable analysis, ENPI was retained in the model as an independent predictor of 5‐year LRC (P = 0.028), DFS (P = 0.011), and OS (P = 0.034) rates. CONCLUSION: Compared with IPNI, the presence of EPNI in OCSCC portends less favorable outcomes. Patients with EPNI are potential candidates for definite aggressive treatment modalities aimed at improving prognosis.