The Prognostic Importance of Midline Involvement in Oral Tongue Cancer

Objectives: To examine the importance of midline involvement and other clinicopathologic factors in predicting the rate of contralateral lymph node metastasis and survival in oral tongue squamous cell carcinoma. Methods: We used Surveillance, Epidemiology, and End Results data to identify a cohort of 5430 patients with laterally rising tumors. Clinicopathologic factors examined as potentially predictive of contralateral lymph node metastasis included extension to midline, T classification, anatomic site, grade, histologic subtype, race, age, and sex. Survival analysis included the above factors plus lymph node status. Results: T1 tumors and lateral T2 and T3 tumors had rates of contralateral lymph node metastasis ranging from 0.7% to 0.9% on presentation. T4 lesions and midline crossing T2 and T3 lesions had corresponding rates of 8.3% to 13.0%. Primary extension across the midline was associated with a mean survival about half that of strictly lateral tumors and its significance was maintained in multivariate analysis. Conclusions: Patients with T1 disease or T2-3 disease that does not cross midline are in a different prognostic class from patients with T2-3 disease that crosses midline or T4 tumors. These results give the strongest evidence to date that involvement of the midline is a powerful predictor for decreased survival in oral tongue squamous cell carcinoma.