Perineural Invasion in the pN0 Neck in OCSCC

Abstract

Objective: Perineural invasion (PNI) has been defined as an intermediate risk factor in OCSCC; however, its effect in the pathologically N0 (pN0) neck remains unclear. The objective of this study is to understand 1) the effect of PNI in pN0 OCSCC patients on outcomes, and 2) the role of adjuvant radiation (XRT).

Method: Retrospective analysis of 90 OCSCC patients treated surgically with pN0 necks after neck dissection at a tertiary care center from 1999-2008. Overall 22% (20/90) were PNI-positive and 40% (36/90) underwent adjuvant XRT. Of those with PNI, 70% (14/20) underwent adjuvant XRT. Primary outcomes were OS, DSS, DFI, and LRC.

Results: There were no differences between the PNI-positive and PNI-negative groups for age, gender, smoking or alcohol status, T-class, margin control, or median follow-up. PNI-positive patients had significantly worse DSS, DFI, and LRC than PNI-negative patients (P = .049, P = .046, and P = .026, respectively), but there was no difference in OS between the 2 groups (P = .15). Multivariate analysis verified PNI to be associated with worse DFI and LRC (P = .02 and P = .006, respectively). Amongst PNI-positive patients, those who received adjuvant XRT demonstrated significantly improved DFI and LRC (mean 6.5 years vs 1.7 years; P = .012 and mean 6.7 years vs 1.9 years; P = .047, respectively). There was no improvement in OS or DSS in those receiving adjuvant XRT.

Conclusion: Perineural invasion portends a worse DSS, DFI, and LRC in this cohort of patients with pN0 OCSCC. Adjuvant radiation significantly lengthens the DFI and improves LRC. Thus, it should be strongly considered for patients with PNI-positive pN0 OCSCC.