2.2. Data Collection

Surgeons were encouraged to prospectively document and collect data on every patient with a head and neck tumor. These data included age, gender, smoking and alcohol consumption, comorbidities, TNM stage according to the 8th “Union for International Cancer Control” Edition, status of T (tumor size and site), of N (regional lymph node involvement) and of M (distant metastasis), grade and histology. Further data included the presence of complications, functional outcomes (e.g., dysphagia), disease-free survival (DFS) status, overall survival (OS) status, the dates of the events, the region of any metastatic disease and the cause of death.