Prognostic Role of Depth of Invasion Stratification Beyond the 10 mm Threshold in Tongue Carcinoma

Objectives: The aim of this study is to define the prognostic role of further stratification in oral tongue and floor squamous cell carcinoma (OTFSCC) with a pathological DOI > 10 mm. Methods: A retrospective multicenter study was conducted on patients with a pDOI > 10 mm. Patients were stratified into three groups based on pDOI values: Group A (11–20 mm), Group B (21–30 mm) and group C (> 30 mm). The association between stratified pDOI and various histopathological features was investigated, along with disease-free survival (DFS), disease-specific survival (DSS), and overall survival (OS). Univariable and multivariable Cox regression analyses were applied to estimate the hazard ratio (HR). Results: A total of 108 patients were included. Seventy-six patients (70.4%) were in Group A, 22 (20.4%) in Group B, and 10 (9.2%) in Group C. The association between the stratified pDOI and ENE (p = 0.004), lymph node burden (LNB) (p = 0.011) and lymph node ratio (LNR) (p = 0.026) resulted statistically significant. Five-year DSS resulted in 72.5% for Group A, 53.3% for Group B, and 25.9% for Group C. Univariable analysis showed that a pDOI > 30 mm was associated with a statistically significant increased risk of recurrence (HR = 8.32, p = 0.000) and mortality from disease (HR = 3.61, p = 0.014). Conclusion: The stratification of OTFSCCs with a pDOI > 10 mm was statistically significantly associated with ENE, LNB, and LNR. Pathological DOI > 30 mm emerged as a negative prognostic factor for DFS and DSS. Level of Evidence: Level 3.