Study Finds Bladder Cancer Risk Not Reduced with Metformin, According to Cancer Monthly

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Researchers say the diabetes drug does not appear to reduce the risk of bladder cancer in patients with type 2 diabetes.

Use of metformin is not associated with a decreased incidence of bladder cancer.

New research conducted at the University of Pennsylvania’s Abramson Cancer Center and reported by Cancer Monthly finds that patients on the popular type 2 diabetes drug metformin (Glucophage) have about the same risk of getting bladder cancer as patients on another class of drugs called sulfonylureas . Both types of drugs carry a lower risk of bladder cancer than thiazolidinediones like Actos (pioglitazone).

The study included 87,600 patients with type 2 diabetes who were part of the Health Improvement Network database in the UK. Because diabetes patients have a slightly increased risk of bladder cancer anyway, the researchers focused only on patients who were new users of either metformin or sulfonylureas (SUs). After adjusting for age, gender, smoking, obesity, and average blood sugar levels, the researchers calculated the number of bladder cancer cases among people on each drug and compared the results.

Among the metformin users, there were 196 cases of bladder cancer. There were 66 cases of bladder cancer among diabetes patients on an SU drug. No difference was found between the two groups based on sex or length of drug use. Summarizing their findings in Diabetes Care, the authors conclude, “Use of metformin is not associated with a decreased incidence of bladder cancer.” They go on to recommend, “Similar methods should be used to study other cancers that have previously been identified as potentially preventable with metformin.”

According to an earlier University of Pennsylvania study, patients treated with thiazolidinedione (TZD) drugs like Actos (pioglitazone) for 5 or more years have been found to have a two-to-three-fold increase in bladder cancer risk compared to those on SU drugs. Diabetes affects about 285 million people worldwide and TZD drugs like Actos account for up to 20 percent of the drugs prescribed for diabetes in the US.

The original Penn Medicine studies were published in Diabetes Care (Mamtani, R, et al, “Incidence of Bladder Cancer in Patients with Type 2 Diabetes Treated with Metformin or Sulfonylureas”, February 4, 2014, Diabetes Care, Epub ahead of print, ) and the Journal of the National Cancer Institute (Mamtani, R, et al, “Association between longer therapy with thiazolidinediones and risk of bladder cancer: a cohort study”, September 19, 2012, Journal of the National Cancer Institute, pp. 1411-1421,

For over ten years, Cancer Monthly has been the only centralized source of cancer treatment results. Patients can see the actual survival rate, quality-of-life indicators, and other key data for approximately 1,500 different cancer treatments. Cancer Monthly provides timely and ground-breaking news on the causes, diagnoses and treatments of the most common cancers including Bladder, Brain, Breast, Colon, Kidney (Renal), Liver, Lung (NSCLC), Ovarian, Prostate, and Rectal Cancers, Melanoma, Mesothelioma, and Non-Hodgkin's Lymphoma. Written for patients and their loved ones, Cancer Monthly helps families make more informed treatment decisions.

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Michael Ellis
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