OBJECTIVES: We investigate if sublingual space invasion (SLI) determined on magnetic resonance imaging confers differences in clinicopathological manifestations and treatment outcomes of oral tongue squamous cell carcinoma (OTSCC). STUDY DESIGN: Retrospective cohort study. SETTING: Tertiary Academic Medical Center. METHODS: 221 OTSCC patients were included. Cox regression models and Kaplan-Meier methods were used, and nomogram construction was performed, incorporating SLI with other adverse factors, to predict the prognosis. RESULTS: On multivariable analysis, the following were associated with cervical nodal metastasis: (1) greater MRI T classification of T3/T4 versus T1/T2: adjusted odds ratio (aOR) 2.784, 95% CI = 1.459 to 5.313, P = .001
(2) gender (female vs male): aOR 4.117, 95% CI = 1.602 to 10.576, P = .003
(3) presence of MRI-determined SLI: aOR 2.588, 95% CI = 1.393 to 4.808, P = .002. For survival outcomes, extranodal extension (adjusted hazard ratio [aHR]: 3.380, 95% CI = 2.024-5.644, P <
.001), poorly-differentiated type (aHR: 1.720, 95% CI = 1.006-2.943, P = .047), lymphovascular invasion (aHR: 2.100, 95% CI = 1.220-3.614, P = .007), and SLI (aHR: 1.700, 95% CI = 1.086-2.661, P = .020) were statistically significant prognosticators of disease-free survival. In overall survival, when controlled for age, gender, overall TNM stage, Charlson morbidity index, surgical margins, depth of invasion and adjuvant therapy, SLI was a statistically significant prognosticator (aHR: 1.622, 95% CI = 1.012-2.602, P = .044). A proposed novel nomogram for overall survival combining SLI and other risk factors showed a higher concordance index compared to a nomogram with TNM staging alone (0.783 vs 0.629, P <
.001). CONCLUSION: SLI is an independent prognostic factor for treatment outcomes in OTSCC. Incorporating SLI into a novel nomogram demonstrated improved predictive accuracy for post-treatment outcomes.