Metformin and me

Among the various medications I’m taking to supplement the chemotherapy is a drug called metformin. It’s a diabetes drug and I don’t have diabetes. So what am I doing taking this drug?

Our oncologist agreed to prescribe it – which she can do, even though this drug is meant for diabetes, because physicians are allowed to prescribe off-label uses of medications. She agreed because she felt the drug would be safe to take, and it had shown some benefit in pancreatic cancer patients. (Presumably those were patients who were taking metformin because they also had diabetes.) Pancreatic cancer is one of the gastric cancers, and what works against one gastric cancer may work against another. But as to liver cancer, our oncologist said, there wasn’t yet any similar evidence, so she would only prescribe it if we understood that she had absolutely no idea if it would benefit me. That seemed fine to us.

But is the possible benefit metformin brings just a medical coincidence, or is there a reason why a diabetes drug might be of use against cancer? The answer is that there is indeed a reason, and the reason has to do with what’s wrong with cancerous cells. It turns out, as Sam Apple explained in an article in the recent New York Times Magazine focus on cancer, that most cancer cells, to put the point crudely, are extremely hungry, in fact madly voracious. They devour glucose and use it to make more of themselves, or in other words to assemble tumors.

A number of different factors may contribute to this behavior, but Lewis Cantley, who heads the Meyer Cancer Cetner at Weill Cornell Medical College, told Apple that one way to describe what’s going on is that the “insulin … signaling pathway” has “‘gone awry – it’s cells behaving as though insulin were telling it to take up glucose all the time and to grow.’” No less a scientist than James Watson (the co-mapper of DNA), tells Apple that “insulin is pro-cancer.” Watson himself, Apple writes, “takes metformin for cancer prevention; among its many effects, metformin works to lower insulin levels.”

Some or all of this may turn out to be mistaken, Apple notes. But meanwhile he reports that epidemiological studies find that “[d]iabetics taking metformin seem to be significantly less likely to develop cancer than diabetics who don’t – and significantly less likely to die from the disease when they do.”

All of this is good enough for Teresa and me – and that’s why I’m taking metformin.