Metformin causes cancer
Pro Research Analysisby 
Searched over 200M research papers
Consensus Meter
The Relationship Between Metformin and Cancer: A Comprehensive Review
Introduction to Metformin and Its Potential Anti-Cancer Properties
Metformin, a widely prescribed medication for type 2 diabetes, has garnered attention for its potential anti-cancer properties. This interest stems from various epidemiological studies and preclinical data suggesting that metformin may reduce cancer risk and improve survival outcomes in cancer patients .
Metformin and Cancer Incidence
General Cancer Incidence
Several systematic reviews and meta-analyses have investigated the association between metformin use and cancer incidence. A comprehensive meta-analysis found that metformin use was associated with a 31% reduction in overall cancer risk compared to other antidiabetic drugs. This inverse association was particularly significant for pancreatic and hepatocellular cancers . However, the evidence for other cancer types, such as breast, colon, and prostate cancer, was less conclusive .
Site-Specific Cancer Incidence
Pancreatic Cancer
Strong evidence supports the association between metformin use and decreased pancreatic cancer incidence. Multiple studies have consistently shown a significant reduction in pancreatic cancer risk among metformin users .
Colorectal Cancer
The evidence for colorectal cancer is highly suggestive, with several studies indicating that metformin use may improve overall survival (OS) in colorectal cancer patients . However, the association with incidence is less robust, requiring further investigation .
Breast Cancer
The relationship between metformin and breast cancer is complex. While preclinical studies and some observational data suggest a potential protective effect, randomized controlled trials (RCTs) have yielded mixed results, particularly in the metastatic setting . A meta-analysis found no significant association between metformin exposure and breast cancer incidence but did observe a reduction in all-cause mortality among breast cancer patients with type 2 diabetes.
Metformin and Cancer Mortality
Overall Cancer Mortality
Observational studies have shown a significant association between metformin use and reduced cancer mortality. A meta-analysis of observational studies reported a 35% reduction in cancer mortality among metformin users . However, these findings are primarily based on observational data, and more RCTs are needed to confirm these results .
Site-Specific Cancer Mortality
Liver Cancer
Metformin use has been associated with a significant reduction in liver cancer mortality. Studies have shown that metformin users have a lower risk of death from liver cancer compared to non-users .
Lung Cancer
The evidence for lung cancer is less conclusive, with some studies indicating a potential benefit while others do not show a significant association .
Mechanisms of Action
Metformin's potential anti-cancer effects are thought to be mediated through several mechanisms. These include the activation of AMP-activated protein kinase (AMPK), which inhibits the mammalian target of rapamycin (mTOR) pathway, reduction of insulin and insulin-like growth factor-1 levels, and modulation of inflammatory pathways . Additionally, metformin may inhibit cancer stem cells, contributing to its anti-tumorigenic effects.
Conclusion
The current body of evidence suggests that metformin may have a protective effect against certain types of cancer, particularly pancreatic and liver cancers. However, the evidence is less clear for other cancer types, and the results from RCTs have been mixed. While observational studies provide promising data, more high-quality RCTs are needed to confirm metformin's role in cancer prevention and treatment. Until then, the use of metformin as an anti-cancer agent should be approached with caution.
Sources and full results
Most relevant research papers on this topic