Impact of Depth of Invasion in Node‐Negative Oral Tongue Cancer Treated With Surgery Alone

Oral tongue squamous cell carcinoma (OTSCC) is an aggressive malignancy and the most common subsite of head and neck cancer among Taiwanese males. This study aimed to evaluate the prognostic significance of depth of invasion (DOI) in patients with node-negative OTSCC treated with radical surgery alone. We retrospectively analyzed 243 patients with node-negative OTSCC who had undergone radical surgery with adequate margins between 2005 and 2017. Each millimeter increase in DOI was significantly associated with a higher hazard of all-cause mortality (ACM) (hazard ratio [HR], 1.07; 95% confidence interval [CI], 1.03-1.111; p < 0.001), cancer-specific mortality (CSM) (HR, 1.087; 95% CI, 1.04-1.136; p < 0.001) and local recurrence (LR) (HR, 1.081; 95% CI, 1.021-1.145; p = 0.008), but not regional recurrence (RR) (HR, 1.042; 95% CI, 0.986-1.102; p = 0.144). In multivariate analysis, DOI remained an independent predictor of ACM, CSM, and LR. A DOI-based nomogram demonstrated improved predictive performance, with a concordance index of 0.700 for overall survival. In conclusion, DOI represents a crucial prognostic factor for ACM, CSM, and LR in patients with node-negative OTSCC treated with surgery alone, highlighting its potential clinical utility for early risk stratification and guidance in decision-making regarding adjuvant therapy or intensified surveillance.