FDA Still Inconclusive about Lantus Cancer Risk

The review was initiated in July 2009 following publication of four studies suggesting higher cancer rates in patients taking insulin glargine versus other insulin products. 

In an update issued last week, the agency admitted that it had made no headway in determining whether the product was responsible.

"FDA has reviewed the four studies and has determined that the evidence presented in the studies is inconclusive, due to limitations in how the studies were designed and carried out and in the data available for analysis," the announcement said.

In the meantime, the agency is advising patients and physicians that insulin glargine may continue to be prescribed, as long as the label directions and cautions are respected.

One problem with the four studies was that they followed patients for about two years -- "shorter than what is generally considered necessary to evaluate cancer risk from drug exposure," the FDA said.

Additionally, risk factors such as family history of cancer and smoking status weren't tracked consistently nor were previous use of anti-diabetic drugs or changes in medications during follow-up.

"This prevents our ability to attribute the observed cancer risk solely to Lantus," the FDA indicated.

The review also included data from a five-year, randomized trial of insulin glargine and NPH insulin, which showed no difference in cancer rates. But the agency noted that cancer wasn't a prespecified safety outcome.

Sanofi-aventis, which sells insulin glargine, is planning three new epidemiological studies to gauge the cancer risk, the FDA said, with results expected in June of this year.

Another potential source of data is the Veterans Affairs health system, the FDA said. Discussions are now under way between the agencies on whether analyses of the VA patient database would be worthwhile.