Validation of distant metastases risk-groups in oral cavity squamous cell carcinoma patients treated with postoperative intensity-modulated radiotherapy

•This study validated a high DM risk-group in OSCC patients treated with postoperative IMRT with or without concurrent chemotherapy.•Patients with G2-3/pN2-3 were shown to be at high risk of DM and poor survival in the subsequent validation cohort.•Identifying this high risk group may allow alternate treatment strategies to be explored to improve the outcomes.