Blog | Monday, January 9, 2012

More evidence that Lantus causes cancer

There is a new study reported by Bloomberg that "Sanofi's Lantus Doubled Cancer Risk in Study of Diabetics. The study, which was presented at the San Antonio Breast Cancer Symposium retrospectively evaluated medical records of 23,266 patients in southern Sweden and determined that diabetics who used Lantus had a 2.9-fold greater chance of cancer, while those who took the generic drug metformin had an 8 percent lower risk.

I have previously blogged about this back in 2009 when the first reports surfaced about the link between Lantus and cancer. (See "A New Problem With Insulin: Cancer , Lantus Causes Cancer! Why Doesn't Anyone Seem Care?" and "Lantus and Cancer- A Closer Look Is Not Reassuring.")

Back in 2009, when the story broke, the FDA acknowledged the potential link but stated that the data was insufficient and recommended that patients not stop taking Lantus, at least without discussing this with their physicians. They stated that they were "currently reviewing many sources of safety data for Lantus, including these newly published observational studies, data from all completed controlled clinical trials, and information about ongoing controlled clinical trials, to better understand the risk, if any, for cancer associated with use of Lantus."

However, we didn't hear much until January 2011, when they released an update declaring that they had reviewed the four 2009 studies and has "determined that the evidence presented in the studies is inconclusive," and in addition had reviewed results from a five-year study (sponsored by the makers of Lantus) which did not show an increased risk but was "not specifically designed to evaluate cancer outcomes."

They concluded, "At this time, FDA has not concluded that Lantus increases the risk of cancer. Our review is ongoing, including review of information from a current clinical trial." With the new study reported recently, it will be interesting to see whether the FDA chooses to give an update or reveals and additional information, such as a Veterans Administration data set they are supposed to be evaluating.

According to the Bloomberg article, a Sanofi study from Sweden, Norway, Finland, Denmark and Scotland is complete and will be submitted to health authorities this month. In addition, a U.S. study will be finished in early 2012, while a final report from Europe will come later. All of these studies combined will involve more than a million patients, which will hopefully be enough to give a more conclusive answer.

To be clear, I am not 100% convinced that Lantus causes cancer. However, there is another long acting insulin (Levemir) which has similar efficacy to Lantus, has not been associated with cancer, and has a substantially different affinity for the insulin like growth factor (IGF) receptors that are implicated in the possible connection. Given the mounting evidence of a cancer link with an equally effective product that appears to be safer, I can't see any reason to prescribe Lantus when Levemir is available.

Matthew Mintz, MD, is a Fellow of the American College of Physicians. He is board certified in internal medicine and has been practicing for more than a decade. He is also an Associate Professor of Medicine at an academic medical center on the East Coast. His time is split between teaching medical students and residents, and caring for patients. This post originally appeared at Dr. Mintz' Blog. Conflict-of-interest disclosures are available here.