Metformin May Improve Oncologic Outcomes in Bladder CA Patients

Metformin therapy is associated with improved oncologic outcomes among diabetic patients undergoing radical cystectomy (RC) for bladder cancer, researchers reported at the Canadian Urological Association annual meeting in St. John's, Newfoundland.

In a retrospective study of 85 diabetic patients who underwent RC for muscle-invasive bladder cancer (MIBC) and high-risk non-muscle-invasive bladder cancer (NMIBC), Madhur Nayan, MD, of the University of Toronto, and colleagues found that those who used metformin had a significant 62% decreased risk of cancer recurrence and a significant 43% decreased risk of cancer-specific mortality compared with non-users in adjusted analyses. Dr. Nayan's team found no association between metformin use and overall survival. They also found no association between the use of other oral hypoglycemic and insulin and any of the previously mentioned outcomes.

Of the 85 patients in the study, 39 used metformin and 46 did not. The median follow-up was 50 months.

“The present study provides the longest reported follow-up for diabetic patients undergoing RC for MIBC and high risk NMIBC and is the first to demonstrate that metformin use is associated with improved oncologic outcomes in this patient population,” the authors concluded in a poster presentation.

With respect to study limitations, the researchers pointed to the relatively small number of patients and events. In addition, the metformin dose and duration of use prior to surgery was not assessed. The study also did not account for medication changes during follow-up.

In an interview with Renal & Urology News, Dr. Nayan noted that metformin has been evaluated for its chemopreventive effects in various malignancies, and randomized, controlled trials are underway looking at starting metformin in non-diabetic patients to improve their cancer treatment outcomes. Limited research is available, however, on the influence of metformin on bladder cancer outcomes.

“Our study suggests that metformin use among diabetic patients undergoing radical cystectomy is associated with improved relapse-free survival and bladder cancer specific survival,” Dr. Nayan said. “Given that metformin has demonstrated safety among non-diabetics, and given its low cost, further studies are warranted to evaluate potential therapeutic and preventative roles of metformin in patients with bladder cancer.”

At the 2014 American Urological Association annual meeting in Orlando, researchers reported on a study showing that diabetic prostate cancer (PCa) patients who took both metformin and a statin may be at lower risk of biochemical recurrence (BCR) after radical prostatectomy. Matthew Danzig, MD, and collaborators at Columbia University in New York analyzed data from 3,031 patients who underwent RP from 1987- 2010 and who had at least 6 months of follow-up. They excluded patients who received neoadjuvant or adjuvant therapy. The overall BCR rate was 23.7%. Diabetics had a rate of 30.5%, which was reduced to 28.3% with metformin use and 23.5% with statin use. Combined use further reduced the rate to 15%, similar to the 13% rate observed in non-diabetics who were taking statins.

A study published online ahead of print in European Urology found that metformin use is associated with a decreased risk of a prostate cancer diagnosis. In a study of 12,226 men diagnosed with PCa and 122,260 population controls, Mark A. Preston, MD, of Massachusetts General Hospital in Boston, and colleagues found that men who used metformin had a significant 16% decreased risk of a PCa diagnosis in adjusted analyses compared with non-users. Among men who had undergone PSA testing in the previous year, metformin use was associated with a significant 34% decreased risk of a PCa diagnosis. Diabetics on no medication or on other oral hypoglycemic agents did have a significant decrease in the risk of a PCa diagnosis.

The researchers identified study subjects using the Danish Cancer Registry and the Aarhus University Prescription Database.

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