Endpoints
Local recurrence was defined as at least carcinoma in situ of the laryngeal mucosa on the ipsilateral or contralateral laryngeal side after complete removal of tumor with microscopically and histologically negative margins at the initial surgery. The 5-year overall survival (OS) was defined as the interval between surgery and the date of the last consultation or death. The 5-year disease-free survival (DFS) rate was defined as the percentage of patients who were alive and cancer-free at 5 years after the date of the initial surgery.