Popular Diabetes Rx May Not Cut Bladder Cancer Risk

Type 2 diabetes medication metformin may not affect bladder cancer

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Widely given to patients with type 2 diabetes, metformin has been linked to reducing the risk for many types of cancers. The medication, however, may not be effective against one certain cancer.

Metformin, taken alone or with other medications, not only helps control blood sugar, it may offer protection from cancers of the breast, colon, liver, pancreas and prostate, according to scientific research.

Despite that previous research, a new investigation has found that metformin may have no effect on bladder cancer.

"Ask a pharmacist how metformin may lower cancer risk."

Ronac Mamtani, MD, assistant professor of medicine with the Abramson Cancer Center of the University of Pennsylvania and attending physician in hematology-oncology at the Philadelphia Veterans Affairs Medical Center, and his fellow scientists reviewed data on 71,472 diabetes patients who were taking metformin and 16,128 patients who were taking sulfonylureas, another type of medication used to treat diabetes.

These scientists identified 196 patients with bladder cancer in the metformin group and 66 with bladder cancer in the sulfonylureas group.

Some evidence has suggested that people with diabetes are at a higher risk for many forms of cancer. Recent studies have also found that those who take pioglitazone (brand name Actos) to treat diabetes may heighten their likelihood of getting bladder cancer.

Because metformin (brand names Glucophage, Glucophage XR) has been shown to inhibit cancer cell growth, the treatment has been viewed by some as a potential treatment for bladder cancer.

After an average follow-up of two years, however, Dr. Mamtani and colleagues found no evidence that metformin could decrease the risk of bladder cancer in patients with type 2 diabetes.

Dr. Mamtani and his team also looked at duration of treatment and found that it did not influence the cancer rate. Whether metformin was given for five or more years or for less than one year, the risk for bladder cancer remained the same.

“Despite not observing a cancer prevention effect, our results should not detract others from investigating the therapeutic potential of metformin on bladder cancer progression among patients with known bladder cancer,” wrote the authors of this study.

They underscored that metformin has been shown to slow tumor growth by inhibiting a protein that regulates cell growth called mTOR.

“Recently, inhibition of mTOR has demonstrated antitumor activity in a subset of patients with advanced bladder cancer,” added the authors.

This study was published online on February 4 in Diabetes Care. This research was supported by the National Institutes of Health.

Review Date: 
February 17, 2014
Last Updated:
February 18, 2014