Abstract:

The prognostic validity of the TNM staging system for oral squamous cell carcinoma (OSCC) has been widely debated. The 8th edition of the TNM system introduced depth of invasion (DOI) as a new criterion for determining the T category, leading to reclassification of a considerable percentage of early tumors.
Objective: This study aims to compare the prognostic performance of TNM 7 and TNM 8 in a homogenous cohort of 57 cases of early-stage OSCC of the oral tongue.
Materials and Methods: Medical records were reviewed and all cases were staged independently according to TNM 7 and TNM 8 criteria. Statistical analysis included Kaplan-Meier survival estimates, log-rank tests, Cox regression, and ROC curve evaluation.
Results: In TNM 7, 75.4% were classified as pT1 and 24.6% as pT2. Under TNM 8, 59.6% remained pT1, 31.6% became pT2, and 8.8% were upstaged to pT3. The survival analysis showed that TNM 8 provided clearer stratification of survival outcomes, especially distinguishing pT3 from lower stages with statistical significance (p < 0.001). ROC analysis revealed better discriminatory capacity for TNM 8 (AUC = 0.671) than for TNM 7 (AUC = 0.605). Conclusion: While both systems differentiate survival risk in early OSCC, TNM 8 offers improved prognostic accuracy by incorporating DOI. However, it still demonstrates only moderate performance in risk stratification. These findings support the use of TNM 8 for better prediction of mortality in early oral tongue carcinoma, although further enhancements in staging criteria may still be warranted. Keywords: oral tongue cancer, squamous cell carcinoma, histologic risk model, Brandwein-Gensler, prognosis, survival, occult metastasis