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Metformin Might Reduce Gastric Cancer Risk

Summary and Comment |
April 24, 2014

Metformin Might Reduce Gastric Cancer Risk

  1. David J. Bjorkman, MD, MSPH (HSA), SM (Epid.)

In a retrospective analysis, using metformin for >3 years reduced gastric cancer risk by 43% in patients with type 2 diabetes who did not use insulin.

  1. David J. Bjorkman, MD, MSPH (HSA), SM (Epid.)

The oral antidiabetic drug metformin has demonstrated anticancer activity in limited studies. To investigate whether metformin use is associated with reduced risk for gastric cancer, researchers in Korea used national insurance claims data to retrospectively assess cancer incidence in metformin users versus nonusers among 40,000 patients with type 2 diabetes. Among a total of 7000 regular insulin users, 5900 had used metformin, and among 33,000 insulin nonusers, 27,000 had used metformin.

Gastric cancer incidence was lower in patients taking metformin compared with those not taking metformin among insulin nonusers (P=0.047) but not among regular insulin users. In a multivariate regression model, longer duration of metformin use was associated with reduced risk for gastric cancer (adjusted hazard ratio, 0.88; 95% confidence interval, 0.81–0.96). In a second model that assessed duration of use in blocks of time, metformin use >3 years was associated with reduced risk for gastric cancer (adjusted HR, 0.57; 95% CI, 0.38–0.87).

Comment

A few study limitations should be noted. The overall and annual data analyses barely achieved statistical significance. Also, because of inherent confounding in retrospective database studies, results should be interpreted with caution. Compared with the main findings, those showing reduced cancer risk with long-term use of metformin are more compelling and consistent with reduced risks for cancers in other studies. However, perhaps most compelling was the finding that gastric cancer risk was doubled in insulin users versus nonusers, regardless of metformin use. Understanding the mechanisms by which both insulin and metformin might affect cancer risk requires additional study.

  • Disclosures for David J. Bjorkman, MD, MSPH (HSA), SM (Epid.) at time of publication Leadership positions in professional societies World Gastroenterology Organization (Treasurer)

Citation(s):

Reader Comments (7)

* * Other, Other, hyderabad

The journel is very informative and helopful

Dr. V Kantariya MD Physician, Family Medicine/General Practice

Diabetes Drug Metformin May Fight Cancer! Metformin slows prostate cancer grouth in adjuvant setting (AACR, 103rd Annual Meeting2012), boosts survival in ovarian cancer(Mayo Clinic,2012),exhibits
antineoplastic effect in patients with thyroid cancer (J.Clin.Endoerinol Metab.2013).More Study Needed!

Dr. V Kantariya MD Physician, Family Medicine/General Practice

Metformin was found to reduce risk in pancreatic and colon cancers in patients with type 2 diabetes in an epidemiologic study (EASD 45th Annual Meeting,2009). Metabolic Syndrome (MetS) is a risk factor for gasrtointestinal neoplasms.Metformin may control the presence of any components of MetS,

Dr. Octavio Castillo y L FICS, PhB Physician, Surgery, General, Puebla, Mex

Despues de tantas malas notocias, una buena para los diabeticos,

David J. Bjorkman, M.D., M.S.P.H., S.M. Physician, Gastroenterology

The risk of cancer in patients taking metformin, but not insulin, for 3 years was 0.37% compared to 0.49% for those not taking metformin for an unadjusted ARR of 0.12% a RRR of 25% and a NNT of 8.3. The difference increased with time with the risk for metformin users at 7 years being 0.94%, compared to 1.25% for nonusers (ARR=0.31%, RRR=25%, NNT=3.2).

Tim Beer, MD Physician, Internal Medicine

What was the ABSOLUTE risk reduction?

David Bjorkman, M.D., M.S.P.H., S.M. Physician, Gastroenterology

I misplaced the decimal place for the NNT in my prior comment. The correct information for patients not taking insulin is a cancer rate at three years of 0.37% for those on metformin compared to 0.49% for others (ARR 0.12%, RRR 25%, NNT 833). It increases to 0.94% compared to 1.25% at 7 years (ARR 0.31%, RRR 25%, NNT 323).

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