The other day, my friend Bill showed me an article in a magazine called “Life Extension” that touted the benefits of the anti-diabetic drug metformin (also known as Glucophage) in preventing cancer. Naturally I was skeptical. The magazine also promotes (and markets) vitamins, nutritional supplements, anti-aging treatments and all sorts of stuff to prevent disease.
But Bill is a smart guy, not easily fooled. So I read the article and more importantly, looked at its sources. To my surprise, the article referenced lots of high-class articles in real scientific journals. Metformin turns out to be a hot item!
I started reading and this is what I learned. Almost all the evidence for cancer prevention by this drug comes from studies of people with diabetes. Now diabetics are known to have higher rates of certain cancers, namely liver, pancreas, endometrium, colon/rectum, breast, and bladder. There is lots of speculation why this happens. Much of this is speculation revolves around two issues. One is the higher blood sugar in these people – sugar feeds cancers. The second is the higher amounts of insulin in their blood. Yes, people with type 2 diabetes, the kind we see in overweight adults have higher than normal amounts of insulin in their blood. Their problem is they can’t use it properly – they are relatively insensitive to insulin.
Another related but different cause of cancer in diabetics is that they are generally overweight. Being overweight is the second major reversible risk factor for cancer after smoking. That too may relate to higher levels of insulin. It turns out that insulin has a close chemical cousin called insulin-related growth factor that many investigators think promotes cancer growth. So that may explain the insulin-cancer connection.
So what about metformin? In November of 2010, a large study of metformin and cancer was published in the journal, Cancer Prevention Research. This was a meta-analysis, meaning the authors reviewed and reported on all the well-documented studies of metformin and cancer in diabetics. They found that diabetic patients treated with metformin were about 25 percent less likely to develop or die from the typical cancers found in diabetics.
The reason metformin reduces the cancer rate isn’t known. Scientists think it may relate to lower blood insulin levels or some interference with the cancer cells ability to use glucose, but that is all speculation. We also know that metformin will slow cancer cell growth in test tubes and in mice.
The big question is whether it will block cancer growth in non-diabetic people. We don’ t know. And metformin is not an innocuous drug. It does interfere with our metabolism – good for diabetics but who knows for non-diabetics?
One problem for the future in studying the drug is that it is available as a generic – cheap – so no big drug company will put out the money to test its ability to prevent cancer. But, there is hope. The National Cancer Institute is sponsoring a study where metformin is being added to the usual drugs in patients with early stage breast cancer to prevent the cancer from coming back. Half the patients will get metformin and the rest will receive a placebo.
But until we learn the results of this study – in maybe 5-10 years – I would forget about the drug. We just don’t know if it will work and it may be harmful – unless of course you have adult-onset diabetes.
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4 comments:
Doc,
I am a big metformin fan. Please do some more research and you will find positive effects on alzheimers, heart problems, obesity, endometrial cancer, lung cancer, and most significantly, aging.
Did you know if you feed a C. Elegans worm with metformin it will live longer. Same thing with mice.
Did you know that all centenarians show high insulin sensitivity?
All the positive metformin results point to the reduced insulin needs of those who take the drug. I am a Type I diabetic with no insulin sensitivity issues. I have been taking metformin for 15 years and my daily insulin use is lower by 20%.
Insulin is toxic over time. If you can get by with less, there are significant health advantages that outweigh the very marginal risks of metformin. Did you know that it has a billion-man-year plus therapuetic history? This is a miracle drug which should be taken by everyone over 40, in my layman's opinion. Unless the patient is in End Stage Renal Failure anyway!
I would recommend waiting for actual clinical trials. There are innumerable drugs or compounds that have been touted as cancer preventers or even cures that have failed when subjected to clinical trials. In the late 70's I participated in one on megadoses of Vitamin C, which had been touted as the ultimate cancer treatment by the Nobel prize winner Linus Pauling. At the end of the trial no benefit was found.
My daughter just had surgery (partial hysterectomy) for endometrial cancer as a result of atypical hyperplasia. She'd been receiving progesterone therapy that, obviously, did not work. I am a type II diabetic and although she's not been diagnosed she probably has a proclivity to the disease. Of course we are all concerned about the possibility of a recurrence of the cancer. She's been diagnosed with Stage I. Would you consider the use of metformin for her even though it hasn't been clinically proven? My concern is that she still has her ovaries; isn't she then prone to continued excess estrogen? Thank you.
She should be cured if it was stage one and needs no further therapy. I definitely would not use metformin in any circumstance
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