When oral cancer occurs, there is a possibility that carcinoembryonic antigen (CEA) levels may be elevated. Among the current mainstream tumor markers, CEA is the most broadly applicable. Elevated levels of CEA can occur in a variety of tumors. However, an increase in CEA does not necessarily mean that oral cancer is present. Due to the relatively superficial location of the oral cavity, specific physical examinations of the mouth, or direct visualization of the inside of the mouth using auxiliary instruments, can be used to detect lesions associated with oral cancer. Once oral cancer is diagnosed, the primary treatments are surgery and radiotherapy. After surgery and radiotherapy, adjunctive chemotherapy can be used to improve treatment efficacy.