Postoperative radiotherapy is dispensable for OSCC patients with micrometastases in lymph nodes.

Lymph node metastasis is a decisive factor for performing postoperative radiotherapy for oral squamous cell carcinoma (OSCC). However, whether OSCC patients with only micrometastasis need postoperative radiotherapy is unclear. In this study, OSCC patients (n = 311) with negative (n = 247), only micrometastasis (n = 44) and macrometastasis (n = 20) were detected and selected by HE staining. Micrometastasis was re-assessed using immunohistochemical staining of cytokeratin (CK) in HE-negative patients to find out the false negative cases. The results indicated that, among the negative lymph node cases (n = 247), the positive rate of CK was 4.94% (n = 12). Besides, the clinical features of the primary tumor in relation to the only micrometastatic status and the value of the postoperative radiotherapy on the only micrometastasis patients were evaluated. Patients with only micrometastasis had higher T stage and inferior worst pattern of invasion (WPOI) than patients without micrometastasis, but they had longer overall survival (OS), metastasis-free survival (MFS), and disease-free survival (DFS) than macrometastasis patients. However, the survival time of only micrometastasis patients with or without postoperative radiotherapy was comparable, even in patients with inferior WPOI. Radiotherapy, however, may only benefit patients with IV/V levels of micrometastasis. These data indicated that postoperative radiotherapy is dispensable for only micrometastasis OSCC patients.