Importance Esophageal squamous cell carcinoma (ESCC) carries a poor prognosis, stressing the need for preventive measures. A decreased risk of ESCC among metformin users has been suggested, but evidence is limited. Objective To assess whether metformin use, given its potential anticancer properties, is associated with risk of ESCC. Design, Setting, and Participants This population-based case-control study set between 1994 and 2023 looked at data from all 5 Nordic countries (ie, Denmark, Finland, Iceland, Norway, and Sweden). Participants were patients newly diagnosed with ESCC during the study period, and each was compared with 10 times as many control participants randomly selected from the general population (matched by age, sex, calendar year, and country). Exposures Use of metformin vs nonuse. Main Outcomes and Measures Conditional logistic regression provided odds ratios (OR) with 95% CIs for the association between metformin use and the development of ESCC. In addition to the matching, the ORs were adjusted for tobacco smoking, alcohol overconsumption, use of nonsteroidal anti-inflammatory drugs or aspirin, and use of statins. A dose-response analysis was conducted among participants with at least 5 years of observation time, based on the defined daily dose during the 5-year period. Results This study included 13 050 case patients with ESCC (8030 men 61.5% and 5020 women 38.5%, diagnosed at a median age of 70 years IQR, 62-77 years), and 130 500 age- and sex-matched control participants. Metformin use was associated with a 36% lower odds of ESCC compared with nonuse (OR, 0.64; 95% CI, 0.59-0.69). The odds were especially lower in participants with a higher dosage of metformin (gt;1278 defined daily dose in 5 years: OR, 0.52; 95% CI, 0.44-0.61). Conclusions and Relevance In this case-control study, metformin use was associated with substantially lower odds of ESCC. This finding should prompt investigations of metformin as a preventive option in high-risk individuals and as a potential future therapeutic agent for ESCC.
Xie et al. (Mon,) studied this question.