Hi, I’m Dr. Mark Scholz.

At the PCRI we get questions about supplements, and one of the most common ones is related to Metformin.

Metformin is a prescription medicine (now generic, it has been out for decades) that is used by diabetics to lower blood sugar levels. It’s very popular. It’s a relatively safe diabetic medicine because with many diabetic medicines you’ll see sometimes a marked decline in blood sugar levels. Metformin doesn’t do that as commonly, and people that don’t have serious diabetes can start out on Metformin.

There have been a number of retrospective trials because Metformin is used so commonly you can look at people that have both diabetes and prostate cancer simultaneously. There are a variety of other options for diabetes besides Metformin, so researchers have looked at men with prostate cancer and diabetes who have either received Metformin or some other type of treatment for their diabetes, and then they’ve compared survival rates over time. In these studies, the men that were treated with Metformin lived longer (in relation to their prostate cancer) than the men that were treated with other types of diabetic medications.

One answers, “Why did they even look at Metformin? Why did they even study the question?” Well there’s some logical reasons to consider given that Metformin is known to lower insulin levels. Insulin functions kind of like growth hormone and can stimulate cancer growth. So taking Metformin to lower insulin logically might slow the progression of prostate cancer.

So when this was looked at retrospectively in large data-based type trials the men getting Metformin did indeed do better. The problem with these trials is we don’t have one that is testing Metformin as an isolated factor. That’s what a prospective trial is. So even though several retrospective trials show an advantage for Metformin over other diabetic medications we don’t really have a conclusive trial showing that everyone with prostate cancer should take Metformin. But considering that Metformin is a fairly mild agent, you can get it from your family doctor and he can monitor you. It’s inexpensive. And certainly men with higher-risk prostate cancer in the Azure or Indigo categories or the Royal categories need every advantage they can get. Metformin might be a logical thing to consider in that particular scenario, and the downsize seems to be fairly limited.

So while the studies that have been published have been done exclusively in men that have diabetes, it seems logical to some people although we don’t have any medical proof that Metformin might even be helpful in men that don’t have diabetes. In my own practice I tend to think of using Metformin in my prostate cancer patients who have more serious types of prostate cancer and perhaps those that are overweight. One of the side benefits of Metformin is that we will see some weight loss in some of the individuals that take this medicine. So Metformin for prostate cancer in men that don’t have diabetes has so far not been proven in a prospective trial to be beneficial, but there are logical reasons to believe that Metformin might be beneficial even in men without diabetes, and since its a mild agent some doctors considering using it in this setting.