Impact of Perineural Invasion in the Pathologically N0 Neck in Oral Cavity Squamous Cell Carcinoma

Objective Patients with oral cavity squamous cell carcinoma (OCSCC) undergo adjuvant radiation for pathologically high-risk features including positive nodal disease and extracapsular spread (ECS). In the absence of these high-risk features, our objective was to determine if perineural invasion (PNI) is an independent risk factor and if adjuvant radiation (XRT) improves disease control rates. Study Design Historical cohort analysis. Setting Tertiary university hospital. Methods Eighty-eight OCSCC patients (46 males, 42 females; mean age = 56.7 years; median follow-up = 4.6 years) treated surgically with pathologically N0 (pN0) necks were studied. Overall, 23% (20/88) were pN0/PNI+ and of those with PNI, 70% (14/20) underwent XRT. Survival analysis using Kaplan-Meier followed by multivariable Cox models was performed. Results Multivariate analysis verified PNI to be associated with worse disease-free interval (DFI) (P = .012) and local-regional control (LRC) (P = .005) and perivascular invasion (PVI) associated with worse DFI (P = .05). Among pN0/PNI+ patients, those who received XRT demonstrated significantly improved DFI (mean = 6.5 years vs 1.7 years; P = .014) and LRC (mean 6.7 years vs 1.9 years; P = .047). There was no improvement in overall survival (P = .68) or disease-specific survival (P = .8) in those receiving XRT. Conclusions PNI is an independent adverse risk factor in the absence of nodal metastasis and extracapsular spread. We observed a statistically significantly longer DFI and LRC when patients were treated with adjuvant radiation.