Diabetes Forecast

Does Lantus Cause Cancer?

I did a Google search on the side effects of Lantus, and one site I found said Lantus may cause cancer. I have type 1 diabetes and have taken Lantus as my basal insulin for about five years. It works pretty well, but now I'm starting to worry. A coworker, who also takes Lantus, may have throat cancer. Could they be connected? Gaoying Vigoa, Roseburg, Oregon

Sue Kirkman, MD, responds: There is no clear evidence that Lantus, or any other insulin or diabetes medication, causes cancer. In the summer of 2009, four research papers about diabetes medications and cancer risk were published in the journal Diabetologia. All four studies were from European countries and looked at existing data on large groups of people. Some, but not all, of the studies suggested that people who took Lantus had a higher risk of some forms of cancer, especially breast cancer.

There has been disagreement in the medical and scientific community about the ways the study results were analyzed, and whether the findings are "real" or not. As with any observational study, even if a higher risk of cancer was seen in people who take Lantus, that doesn't mean that Lantus caused the cancers. It may be that some other risk factor for cancer was more common in Lantus users than in those who didn't use it. The best way to account for these so-called confounding variables is through a randomized controlled trial, where people are assigned to one treatment or another through a random process that is like flipping a coin. If the study is large, the confounding factors, even if we don't know what they are, should be found in roughly equal proportions in both groups. There have been a number of randomized trials comparing Lantus to another form of insulin, and none of them have shown higher rates of cancer in people assigned to take Lantus, so this is reassuring.

Independent of Lantus or other diabetes medications, there is evidence that people with diabetes, especially those with type 2, may be at higher risk of some forms of cancer, such as colon cancer and breast cancer. The reasons for this are not clear, but possibilities include the links between type 2 and overweight/obesity (itself a risk factor for cancer), high blood glucose levels, or insulin resistance. No studies have suggested any link between throat cancer and diabetes (or Lantus).

In short, I don't think you should be concerned about your therapy, especially if it is working well for you. Like all adults, people with diabetes should get recommended cancer screenings and should try to avoid known risk factors for cancer, such as smoking, obesity, and physical inactivity.



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