Comparative outcomes in oral cavity cancer with resected pT4a and pT4b

Objectives: We have previously shown that the resection outcomes of cT4a and cT4b oral cavity squamous cell carcinoma (OSCC) are comparable, but whether similar conclusions can be applied for the pathological stage of this disease needs investigation. In this study, we sought to compare the outcomes and to identify the risk factors for both pT4a and pT4b tumors. Methods: We retrospectively examined 181 pT4 OSCC patients who had radical resections between 2003 and 2010. The 5-year control and survival rates were the main outcome measures. Results: Of the 181 resected pT4 OSCC patients, 133 (73%) had pT4a disease, and 48 (27%) had pT4b disease. All of the resected T4b tumors were below the mandibular notch (infra-notch pT4b). The 5-year outcomes of the patients with infra-notch pT4b and pT4a were comparable: local control, 80% vs. 78%, p = 0.7275; neck control, 87% vs. 82%, p = 0.4798; distant metastases, 22% vs. 23%, p = 0.8871; disease-free survival, 63% vs. 55%, p = 0.2813; disease-specific survival, 68% vs. 60%, p = 0.3526; and overall survival, 62% vs. 44%, p = 0.2643, respectively. Extracapsular spread was the only independent prognostic factor for 5-year survival rates in pT4a patients. Poor tumor differentiation and pN2 status were the independent 5-year survival prognostic factors for the infra-notch pT4b tumor patients. Conclusions: Infra-notch pT4b had outcomes comparable with those of pT4a tumors, although they displayed different risk factors. We therefore recommend that resectable infra-notch pT4b tumors should be classified as pT4a disease in the AJCC tumor staging.