Metformin, a commonly prescribed diabetes drug, may inhibit cell proliferation and decrease cancer risk
October 23, 2013

Prostate cancer (PC) is the most commonly diagnosed cancer and accounts for more than 25% of all new cases. It is also the greatest cause of cancer-related death in Canadian men. The prevalence of diabetes is also high; it affects approximately 285M people worldwide and more than 9M Canadians. It is expected that more men will be diagnosed with both diabetes and PC as diabetes becomes more widespread.
Metformin, a commonly prescribed diabetes drug, helps to reduce blood sugar levels. There is increasing evidence to suggest that metformin inhibits cell proliferation and decreases cancer risk. A few studies have also associated
metformin with decreased rates of PC incidence. However, there have been no comprehensive studies examining the effects of metformin on PC outcomes.
To address this, TGRI Senior Scientist Dr.David Urbach and OCI Cancer Clinical Research Unit Member Dr. Neil Fleshner conducted a population-based retrospective study to examine the effects of metformin use on PC mortality. Using data available through Ontario’s health care administrative databases, the researchers compared more than 3800 diabetic patients who subsequently developed PC. The research team also limited the study population to patients with lower comorbidities and excluded patients with severe
diabetes in order to have a more homogenous study population. Study patients were also categorized based on whether their PC was localized to the prostrate or at a more advanced stage.
A comparative analysis between patients that used metformin and those that did not revealed that cumulative use of metformin after PC diagnosis was associated with a  significant decrease in PC-specific mortality as well as a decrease in overall mortality. This trend was observed even in patients with advanced PC and was dependent on the metformin dose. Other diabetes drugs examined in the study, such as insulin and sulfonylurea, did not have a similar effect.
Explains Dr. Fleshner, “Unlike some cancers, PC is slow-growing therefore medications taken post-diagnosis may have an impact on disease progression and survival. Our data suggests that metformin should be considered as a firstline therapy among patients with PC and diabetes—not just for diabetes control but also to improve cancer prognosis and survival. Metformin may also be ideal for treating PC patients prior to disease recurrence as it is inexpensive, safe and well-tolerated.”
Metformin use and all-cause and prostate cancer-specific mortality among men with diabetes. Margel D, Urbach DR, Lipscombe LL, Bell CM, Kulkarni G, Austin PC, Fleshner N. Journal of Clinical Oncology. 2013 Aug 5.
This study was supported by the Institute for Clinical Evaluative Sciences (ICES), which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care
Source: TrailScribe, September 2013
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