A Bidirectional Study of Individualized Postoperative Adjuvant Treatment Decision Model for Locally Advanced Head and Neck Squamous Cell Carcinoma Based on Multimodal Dynamic Data

Inclusion Criteria: * Age \>= 18 years. * Patients diagnosed and treated at Nanfang Hospital, Southern Medical University or its cooperative hospitals between January 2017 and December 2025. * Patients who either seek medical treatment after June 2022 or sought medical treatment before that but have not lost contact with the hospital for more than 1 year are required to sign the informed consent form voluntarily. * Newly diagnosed head and neck squamous cell carcinoma (HNSCC) confirmed by histopathology. * Locally advanced disease without distant metastasis. * Complete clinical data (including patient demographics, tumor characteristics, treatment details, and prognostic variables). * Availability of MRI, CT, or PET-CT images before and after radical treatment. Exclusion Criteria: * History of or coexisting secondary malignancies. * Lack of definitive radical treatment. * Absence of baseline or follow-up imaging (MRI/CT/PET-CT). * Investigator-determined unsuitability for study participation.