Common diabetes drug, metformin, appears to reduce cancer risk

Keith Block, MD

 Metformin, a commonly prescribed drug for the treatment of type 2 diabetes, has been touted in several recent studies as having the potential to reduce the risk of cancer in people taking it to control their disease. 

 Metformin (Glucophage) helps control both insulin levels and the amount of glucose produced by the liver.  It’s given to people with type 2 diabetes who have not been able to control the disease through lifestyle changes – diet and exercise.

 Since type 2 diabetes affects millions of people and those numbers continue to rise – even among children and teenagers – there is a lot of scientific interest directed toward this population. It has been observed that those taking metformin to control their disease also seemed to have less risk for certain cancers. Moreover, lab studies have shown an association between metformin and its ability to cause the death of cancer cells.

Researchers led by Dr. Diego Espinoza-Peralta, with Mexico’s National Institute of Medical Sciences and Nutrition, presented the findings of their study “Cancer Risk in Diabetes Type 2 Patients Receiving Metformin. Systematic Review and Meta-Analysis,” on June 24, 2012, at the Endocrine Society’s 94^th Annual meeting in Houston.

 Seven studies, encompassing more than 32, 000 patients were reviewed. Researchers concluded that those using metformin on a daily basis to control diabetes were 38% less likely to get any type of cancer relative to those not taking the diabetes drug. This adds to the growing evidence that metformin brings more benefits to diabetic patients beyond glucose control.

 This presentation follows other recent studies and articles about metformin and cancer. The June 11 issue of the Journal of Clinical Oncology contained a study by Rowan T. Chlebowski et al, “Diabetes, Metformin and Breast Cancer in Postmenopausal Women” that looked at the long-studied population of the Women’s Health Initiative. Of 68,019 post-menopausal women in the study, 3,401 had been diagnosed with diabetes. They were observed for nearly 12 years. The researchers compared breast cancer that developed in women with diabetes who used metformin, to the same patient population who did not use metformin. They also compared these groups to women who developed breast cancer and were not diabetic and therefore, were not using metformin. This research showed an association between lowered risk among women with diabetes taking metformin, and the development of invasive breast cancer.

An editorial in the same issue of JCO by Pamela J. Goodwin, and colleagues noted that these and other studies point to a need for further research of both the relationship of diabetes to cancer risk, as well as the use of metformin in lowering risk and as a potential treatment.

A preclinical trial presented by Christopher Heeschen, MD, PhD, at the American Association for Cancer Research’s Pancreatic Cancer: Progress and Challenges conference held last month showed that treatment with metformin caused the death of pancreatic stem cells.

So why is this research important?  Cancer stem cells appear to be the primordial cancer cells that not only survive most treatments but are responsible for recurrent and progressive disease. To date, there is a very limited number of known compounds able to inhibit or kill these critical malignant survival cells.  Additionally, the research suggests that not only does metformin appear to reduce the risk for developing cancer in diabetic patients who take the drug, but that it might also help control cancer in this patient population once it has developed. We have known for a long time, that high glucose levels and insulin resistance not only increase a person’s risk for cancer, but can fuel the growth of existing disease. 

At the Block Center, we emphasize eliminating refined carbohydrates (white sugar, white bread, white rice, etc.) from your diet because research shows that cancer cells have a sweet tooth. We know that they consume 10 – 50 times more glucose than normal healthy cells. In addition, the faster a tumor proliferates, the more glucose it consumes. Experiments have shown that when lab animals are injected with an aggressive cancer, they have much higher survival rates if they have low or normal blood sugar than if they have high blood sugar; glucose enables the cancers to grow with reckless abandon.  

Patients who come to us with a diagnosis of cancer and who are also battling type 2 diabetes are encouraged to adhere both to our diet recommendations and their medication regimen to best prepare them to fight their disease. While the research on metformin suggests it may one day be a widely used adjunct to cancer treatment – and is an off-label treatment strategy we have implemented for certain patients for many years – its current role in keeping diabetes in check and maintaining optimal blood glucose and insulin levels plays an important role in their treatment regimen.

The Life Over Cancer nutrition program features a diet rich in complex carbohydrates such as brown rice, buckwheat, whole-grain bread, wild rice, rye, quinoa, whole wheat pasta and barley. Their high fiber helps dilute, bind, and remove various toxins from the body. In addition, high-fiber foods and whole- grain products prevent the inflammatory and growth stimulating effects of surges in blood sugar and insulin.

So as we cheer the latest metformin studies and know the medication is helping those with type 2 diabetes lower their cancer risk, we must not forget that eliminating refined foods in the first place can not only lower cancer risk, it can also help prevent type 2 diabetes. At the Block Center, our dietary recommendations play an important role in helping boost your natural defenses, curtail inflammation, reduce free-radical damage, minimize platelet activation (which can lead to dangerous blood clotting), and reduce serum levels of insulin-like growth factor 1, (IGF-1), which stimulates cell multiplication and inhibits cell death. 

For more information on The Block Center for Integrative Cancer Treatment, visit BlockMD.com.