Background: Metformin use has been associated with a decreased incidence and mortality of various cancers.

Aim: The aim of this study was to evaluate the association between metformin use and gastric cancer.

Methods: We randomy selected 100,000 type 2 diabetic patients from the 2004 Korean National Health Insurance claim database, and assessed gastric cancer incidence among 39,989 patients (aged 30-97 years) who were regularly treated with anti-diabetic drugs and followed-up from 2004 to 2010. In total, 26,690 patients had used metformin out of 32,978 diabetics who had not regularly used insulin (insulin non-users), and 5,855 patients had used metformin out of 7,011 regular insulin users.

Results: Patients who used metformin showed a lower incidence of gastric cancer than those who did not use metformin, in insulin non-users (P=0.047, log-rank test). However, in patients on regular insulin, there was no difference of gastric cancer incidence according to metformin use. In insulin non-users, the adjusted hazard ratio (AHR) for metformin use was 0.73 (95% confidential interval [CI], 0.53-1.01) with borderline statistical significance (P=0.059). Duration of metformin use was associated with the reduction of gastric cancer risk (AHR, 0.88; 95% CI 0.81-0.96, P=0.003), especially in patients that used metformin for more than 3 years (AHR, 0.57; 95% CI, 0.37-0.87; P=0.009).

Conclusion: Metformin use >3 years in type 2 diabetics who do not use insulin is associated with significantly reduced gastric cancer risk.

Citation Format: Soo-Jeong Cho, Young-Il Kim, So Young Kim, Jong-Hyock Park, Il Ju Choi, You Jin Lee, Eun Kyung Lee, Myeong-Cherl Kook, Chan Gyoo Kim, Keun Won Ryu, Young-Woo Kim. Long-term metformin use reduces gastric cancer risk in type 2 diabetics without insulin treatment: a nationwide cohort study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2136. doi:10.1158/1538-7445.AM2014-2136