Evaluating Depth of Invasion as a Continuous Prognostic Factor in Oral Squamous Cell Carcinoma

Background: Depth of invasion (DOI) has a significant clinical impact on the staging system of oral squamous cell carcinoma (OSCC). We aimed to compare the prognostic impact of treating DOI as a continuous variable rather than a categorical one. Methods: A retrospective review of 277 OSCC patients surgically treated in a tertiary care center from 2000 to 2020, with a minimum 2-year follow-up. The analyses were performed using Cox and logistic regression. Results: DOI as a continuous variable significantly predicted mortality in both univariate (p < 0.001) and multivariate (p < 0.001) analyses. It was also a significant predictor of locoregional recurrence (multivariate p = 0.039) and occult lymph node metastasis (univariate p = 0.005, multivariate p = 0.04). Categorical analysis failed to demonstrate the same significance. Conclusions: DOI as a continuous factor rather than a categorical one is significantly associated with mortality, locoregional recurrence, and occult lymph node metastasis. This innovative approach promotes personalized risk stratification and better decision-making.