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.