4.1. Patient Selection and Data Collection

From 1 December 2011, to 31 December 2013, a total of 141 patients with hypopharyngeal cancer were enrolled in the cohort study. Demographic factors of patients including age, gender, alcohol use, betel nut chewing, and cigarette smoking were documented. Metformin use was based on their previous oral hypoglycemic agents (OHA) administration and persisted through the concurrent chemoradiotherapy (CCRT) treatment until the latest follow-up. The minimal follow-up duration was 4 years. The clinical TNM (tumor, node, metastasis) stage, survival outcome, and disease control were recorded as parameters for further analysis. This study was approved by the Institutional Review Board of China Medical University Hospital, a 2500-bed tertiary teaching hospital in central Taiwan (no. CMUH103-REC1–078). All enrolled patients provided informed consent after a complete explanation of the study protocol. All the clinical data were collected by medical chart review for the patients with hypopharyngeal cancer.