Worst pattern of invasion in oral squamous cell carcinoma is an independent prognostic factor

INTRODUCTION: Biologic aggressiveness of OSCC (Oral Cavity Squamous Cell Carcinoma), has intrigued research in various prognosticating histopathological markers over past few decades. DOI (Depth of Invasion) is one such histopathological factor which affects outcomes and was included in the AJCC 8th edition TNM staging. Pattern of Invasion (POI) has been widely reported as an adverse prognostic factor associated with higher locoregional failure and poor prognosis. However, these factors are not utilized for treatment decision making and for outcome assessment. MATERIALS AND METHODS: This is a retrospective analysis of 320 patients with OSCC who underwent treatment, from October 2018–February 2020. Clinic demographic details were extracted from electronic medical records. Univariate and multivariate analysis was done for the parameters. WPOI (Worst Pattern of Invasion) was correlated with all histopathological prognostic factors. Survival analysis was done using Kaplan Meier for WPOI type's I–V. DFS (Disease free Survival) was evaluated for different grades of WPOI. RESULTS: We analyzed the results comparing, early and advanced T (Tumor) stages, cohesive WPOI I-III, non-cohesive WPOI IV-V. Univariate analysis showed a significant association of T-stage (p = 0.001), N (Nodal) -stage (p = 0.002), DOI (p = 0.008), PNI (Peri-neural invasion) (0.001) and Tumor differentiation Grade (p = 0.001). On multivariate analysis, non-cohesive WPOI (IV & V) showed significant association with grade, PNI, DOI (0.002, 0.033 & 0.033 respectively). Non-cohesive WPOI had significantly higher locoregional failures and short DFS. CONCLUSION: Presence of invasive WPOI is associated with advanced T stage, poor differentiation, PNI, greater depth of invasion, and higher chances of nodal metastasis. WPOI is associated with poor DFS, treatment intensification in early stage disease with WPOI type IV & V may improve survival.