A phase II study has found that metformin slowed the growth rate of prostate cancer in men who were scheduled to undergo a prostatectomy (surgical removal of the prostate).
This finding supports previous research suggesting that the drug may also improve the outcome of men with prostate cancer by interfering with the growth of cancer cells.
"Talk to your oncologist about about medications being studied."
Findings were presented at the American Association of Cancer Research (AACR) Annual Meeting 2012, held March 31-April 4 by Anthony M. Joshua, M.B.B.S., Ph.D., staff medical oncologist at the Princess Margaret Hospital, University Health Network in Toronto.
For this small study, 22 men with confirmed prostate cancer received up to 500 mg of metformin three times a day for about 44 days prior to undergoing prostatectomy. No serious side effects relating to the medication were reported before or after the surgery.
Joshua explained, “This gave us the ability to compare what the prostate cancer looked like when it was first diagnosed to what it looked like when the prostate cancer was removed from the body.
Metformin appeared to reduce cancer growth in some of the men by interfering with "one of the main growth pathways that may have contributed to the overall growth of the tumor,” according to Joshua.
Along with the cancer benefit, the drug also favorably impacted blood glucose levels, body mass index (BMI) and waist-to-hip ratio.
However, a prostate cancer specialist has reservations about this study.
Brian J. Miles, M.D., F.A.C.S., a urologist who specializes in Robotic Radical Retropubic Prostatectomy at Methodist Hospital in Houston, TX, takes issue with this study. "There is evidence that diabetes has been associated with prostate cancer and the theory that metformin, a diabetic drug, can affect prostate cancer is not unreasonable. Unfortunately, it is very early and a very small study of only 22 men," Dr. Miles told dailyRx.
"The notion that it clearly has benefit is not really shown in this study. There is no comparison group and the fact that they were able to measure the effect of metformin on prostate cancer before and after is not possible based on this," said Dr. Miles.
He explained in an email, "When we biopsy prostate cancer patients the final pathology is not infrequently different than the original pathology. The notion that the effect they may have seen on the final specimen was entirely due to metformin could not possibly be proven by this study."
Dr. Miles continued, "The study definitely needs to be repeated in a multi-institutional fashion and a placebo-controlled randomized fashion. That’s the only way that we’re going to see whether it was metformin or whether this was just an unusual finding that’s really not supported in the final analysis.
"I think publishing this is premature at best, and, hopefully, does not have men seeking to suddenly have themselves placed on this antidiabetic drug based on this one small unsubstantiated study," Dr. Miles concluded.
The Princess Margaret Hospital Foundation, the Jewish General Hospital Foundation (Montreal) and the Terry Fox Foundation funded this study.
Scientific findings presented at conferences are considered preliminary until published in peer-reviewed journals.