Decreased risk of esophageal squamous cell carcinoma among metformin users in a population-based cohort study.

Abstract

e15507 Background: Metformin, mainly used in the treatment of diabetes, may prevent various types of cancer, but no study has specifically examined its potential influence on the risk of esophageal squamous cell carcinoma, the major histological type of esophageal cancer. The aim of this study was to determine the association between metformin use and esophageal squamous cell carcinoma. Methods: This was a nationwide population-based prospective cohort study conducted in Sweden in 2005-2015. Among 8.4 million participants identified from the Swedish Prescribed Drug Registry, 411,603 (5%) were users of metformin. The metformin users were compared with 10 times as many frequency-matched non-users of metformin (n = 4,116,030) by age and sex. Multivariable cause-specific proportional hazards model was used to calculate hazard ratios (HR) with 95% confidence intervals (CI), adjusted for age, sex, calendar year, place of residence, tobacco smoking, alcohol overconsumption, and use of non-steroidal anti-inflammatory drugs or statins. Results: The incidence rates of esophageal squamous cell carcinoma were 3.5 per 100,000 person-years among the metformin users and 5.3 per 100,000 person-years in the non-users. Metformin users overall were at a decreased risk of esophageal squamous cell carcinoma compared with non-users (adjusted HR 0.68, 95% CI 0.54-0.85). The decrease in risk was more pronounced in new metformin users who were 56 years old when they started their metformin therapy (HR 0.44, 95% CI 0.30-0.65). Conclusions: Metformin therapy may decrease the risk of developing esophageal squamous cell carcinoma.