Purpose: Aim of the study is to evaluate the role of re-categorization of pathologic T (pT) classification of node negative oral tongue cancer based on the new 8th edition AJCC classification system and its impact on survival based on primary tumor size and depth of invasion (DOI).
Methods: A total of 1277 patients with node-negative oral tongue cancer (diagnosed from 2010-2013) were evaluated in the National Cancer Database (NCDB). A Kaplan-Meier analysis log-rank test was used to compare overall survival by pT classification using the 7th and 8th editions of AJCC. Multivariate analysis with Cox-Proportional Hazards modeling was used to calculate hazard rations (HR) with 95% confidence interval while adjusting for demographic and clinicopathologic confounders.
Based on the 8th edition AJCC, the pT remain unchanged for 1059 patients (82.9%), upstaged in 218 patients (17.1%) and none were downstaged. Using 8th edition AJCC classification, worsening overall survival was noted for pT2 compared to pT1 (HR = 1.43, 95% CI: 1.03-1.98), P = .033. No significant difference was noted between pT1 and pT2 when analysis was based on 7th edition AJCC (HR = 1.19, 95% CI: 0.85-1.65), P = .310. Patients with pT3 disease had no survival difference compared to pT1 using both 8th edition (HR = 0.86, 95% CI: 0.52-1.42), P = .547 and 7th edition (HR = 1.02, 95% CI: 0.53-1.98), P = .949 of the AJCC.
Conclusion: The 8th edition AJCC classification system leads to improved discrimination for overall survival between the pT1 and pT2 subsets, but pT3 category remains problematic in both the staging systems.
Level of evidence: 4