Metformin therapy and risk of cancer in patients with type 2 diabetes: systematic review
Abstract
AIMS/HYPOTHESIS: Diabetes treatments were related with either an increased or reduced risk of cancer. There is ongoing debate about a potential protective action of metformin. To summarize evidence on the association between metformin and risk of cancer and cancer mortality in patients with diabetes. DATA SOURCE: MEDLINE and EMBASE (January 1966-April 2012). We selected randomized studies comparing metformin and other hypoglycaemic agents and observational studies exploring the association between exposure to metformin and cancer. Outcomes were cancer mortality, all malignancies and site-specific cancers. RESULTS: Of 25307 citations identified, 12 randomized controlled trials (21,595 patients) and 41 observational studies (1,029,389 patients) met the inclusion criteria. In observational studies there was a significant association of exposure to metformin with the risk of cancer death [6 studies, 24,410 patients, OR:0.65, 95%CI: 0.53-0.80], all malignancies [18 studies, 561,836 patients, OR:0.73, 95%CI: 0.61-0.88], liver [8 studies, 312,742 patients, OR:0.34; 95%CI: 0.19-0.60] colorectal [12 studies, 871,365 patients, OR:0.83, 95%CI: 0.74-0.92], pancreas [9 studies, 847,248 patients, OR:0.56, 95%CI: 0.36-0.86], stomach [2 studies, 100701 patients, OR:0.83, 95%CI: 0.76-0.91], and esophagus cancer [2 studies, 100694 patients, OR:0.90, 95%CI: 0.83-0.98]. No significant difference of risk was observed in randomized trials. Metformin was not associated with the risk of: breast…
How strong is the evidence?
Evidence Hub reads this as a systematic review, done in people. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid. Reported size: 1,029,389 participants or records.
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