Metformin tied to lower gastric cancer risk after H. pylori eradication

Last Updated: 2018-11-06

By Will Boggs MD

NEW YORK (Reuters Health) - Metformin use is associated with a lower risk of gastric cancer in diabetic patients after eradication of H. pylori, researchers from Hong Kong report.

"Although previous studies had suggested the potential effects of metformin in reducing gastric cancers in diabetic patients, these studies failed to stratify patients according to H. pylori infection statuses, which is one of the most important risk factors for gastric cancer," said Dr. Wai K. Leung from Queen Mary Hospital in Hong Kong.

"This is the first study to demonstrate the gastric chemopreventive effects of metformin in diabetic patients who had received H. pylori eradication therapy," he told Reuters Health by email.

Metformin reduces hyperinsulinemia and insulin-growth factor (IGF) production, both of which have been shown to enhance proliferation of cancer cells that express IGF receptors, but its chemopreventive role in gastric cancer remains controversial.

Dr. Leung's team investigated the potential preventive effect of metformin on gastric cancer in more than 7,000 diabetic patients who had received H. pylori eradication therapy, including 5,368 metformin users.

During a median follow-up of 7.1 years, 37 patients (0.51%) were diagnosed with gastric cancer, for an overall incidence of 7.1 per 10,000 person-years, the researchers report in the Journal of the National Cancer Institute, online October 16.

The risk of developing gastric cancer was 51% lower among metformin users, a significant reduction that translated into 7.60 fewer cancer cases per 10,000 person-years compared with nonusers.

Each one-year increase in metformin use was associated with 15% lower risk of gastric cancer, and there was a dose-related effect of metformin: 27% lower risk for less than 975 cumulative defined daily doses (cDDD) and 67% lower risk for 975 or more cDDD, compared with non-metformin use.

By comparison, the risk of gastric cancer was 19% lower among insulin users (versus nonusers of insulin), but this difference fell short of statistical significance.

Moreover, HbA1c level did not appear to affect gastric cancer risk.

"In diabetic patients, the use of metformin could possibly further reduce the risk of gastric cancer development after H. pylori eradication," Dr. Leung concluded.

SOURCE: https://bit.ly/2JHJ8KU

J Natl Cancer Inst 2018.