Perineural invasion: Independent prognostic factor in oral cancer that warrants adjuvant treatment.

BACKGROUND: Controversy exists regarding the administration of adjuvant radiotherapy (RT) when perineural invasion (PNI) is the only adverse histological feature. The purpose of this study was to evaluate the impact of PNI on the survival of patients with oral cavity squamous cell carcinoma (SCC). METHODS: A retrospective study of 1524 treatment naive patients with oral cavity SCC who underwent surgery from January 2012 to March 2015 was conducted. Survival analysis was performed using Cox regression model. RESULTS: The incidence of PNI was 20.3% and higher in tongue cancers (odds ratio 2.43). The PNI significantly affected both disease-free survival (DFS; hazard ratio [HR] 1.84) as well as overall survival (OS; HR 1.7). Patients with early node-negative oral cavity SCC with PNI are more likely to develop recurrences and have mortality (HR 2.79 for DFS; HR 2.54 for OS). However, the addition of adjuvant radiation in these patients showed improvement in survival (p = .022). Forest plot analysis showed a trend toward poor survival across all subgroups in patients with PNI. CONCLUSION: Aggressive treatment of the primary cancer with the coincident management of the neck is important in the presence of PNI. The PNI worsens survival and warrants intensification of adjuvant treatment.