Background: The eighth edition of the American Joint Committee on Cancer (AJCC) for oral cancer has incorporated additional pathological features like depth of invasion (DOI) and extranodal extension (ENE) into T and N staging. The incorporation of these two factors will impact the staging and, hence, the treatment decisions. The aim of the study was to clinically validate the new staging system in predicting the outcome in patients treated for carcinoma oral tongue. The study also examined the correlation of pathological risk factors with survival.

Methods: We studied 70 patients with squamous cell carcinoma of the oral tongue who underwent primary surgical treatment at a tertiary care center in the year 2012. All these patients were restaged pathologically according to the new AJCC eighth staging system. The 5-year overall survival (OS) and disease-free survival (DFS) were calculated using the Kaplan-Meier method. Akaike information criterion and concordance index were calculated between both staging systems to identify a better predictive model. Log-rank test and univariate Cox regression analysis were conducted to find out the significance of different pathological factors on outcome.

Results: Incorporation of DOI and ENE resulted in 47.2% and 12.8% stage migration, respectively. DOI less than 5 mm was associated with a 5-year OS and DFS of 100% and 92.9%, respectively, compared to 88.7% and 85.1%, respectively, when the DOI was more than 5 mm. Presence of lymph node involvement, ENE, and perineural invasion (PNI) were associated with inferior survival. The eighth edition had lower Akaike information criterion and improved concordance index values compared with the seventh edition.

Conclusion: The eighth edition of AJCC allows better risk stratification. Restaging of cases based on the eighth edition AJCC staging manual resulted in significant upstaging with difference in survival.