Staging of oral cavity cancer in the 8th edition of the TNM classification: the role of computed tomography in the assessment of depth of invasion and extranodal extension

Abstract

Introduction: In the TNM staging (TNM-8) for oral cavity cancers (OCC), depth of invasion (DOI) and extranodal extension (ENE) were added to the T and N pathological classification, respectively. It has been recognized for decades that the prognosis of OCC worsens when the tumor is thicker, but more recent data suggest that DOI is a better predictive parameter than tumor thickness. Objective: Suggest and validate pre-surgical tomographic evaluation criteria for OCC based on the pathological DOI criteria. Methods: A retrospective cohort study was conducted with 80 patients with tongue and floor of mouth tumors, T1 and T2, followed from 2009 to 2015. Patients were initially classified according to the 7th edition of the TNM (TNM-7) using pathological samples and then reclassified based on the updated 8th edition of the TNM (TNM-8) criteria. The same was done radiologically, using extrapolation and adaptation of the pathological criteria to tomographic evaluation. The results of pathological staging were compared and correlated with the main clinical outcomes. The same was done with the radiological results. To evaluate the pre-surgical accuracy of tomographic staging, radiological and pathological results were compared. Results: Regardless of the criteria (TNM-7 or TNM-8), it was observed that computed tomography (CT) with venous contrast may be used to guide the initial staging. Strong positive correlation was observed between tumor thickness and DOI at both CT and pathology. Considerable upstaging was observed in the sample of assessed patients for both criteria. In the comparison between tomographic and pathological T classifications, moderate correlation was observed in relation to thickness and DOI. Conclusion: Computed tomography can be used to evaluate the depth of preoperative invasion in oral cavity tumors according to the criteria established in the present study.