Studies from Germany, Sweden and Scotland, published last Friday in Diabetologia, suggest a “possible link” between the use of Lantus insulin and cancer.
The findings prompted the European Association for the Study of Diabetes to make an urgent call for additional research into the association.
The EASD added that patients who are presently taking the relatively new, synthetic insulin should continue to do so, although some might wish to consider alternative types of insulin.
Human insulin, the older form of the hormone, has been used for decades. Its safety is beyond doubt, according to the EASD. Lantus has been used widely, but only since 2000.
The German study looked at an insurance database containing information regarding 127,000 insulin-treated patients. Scientists found that patients who had used Lantus were more likely to be diagnosed with cancer, and the effect was dose-dependent.
Thus, in patients receiving a dose of 10u, patients taking Lantus had cancer rates that were 9% higher than those taking human insulin. For those receiving 50u, the increased risk associated with Lantus was 31%.
Diabetologia editor Edwin Gale and EASD president Ulf Smith had become aware of the German findings awhile ago, according to an EASD press release. They decided to seek confirmatory evidence prior to announcing them formally.
As a result, similar database-driven studies were carried out in Sweden, Scotland, and the UK.
The Swedish study showed that patients taking Lantus insulin alone had twice the risk of breast cancer. The Scottish study revealed a statistically insignificant increased risk for breast cancer. The UK study was entirely negative.
Gale and Smith, in their press release, emphasize that all the studies have important methodological limitations.
In particular, patients taking Lantus insulin tended to be older, more obese and to have higher blood pressure than those receiving other forms of insulin. These pre-treatment differences could by themselves explain any differences in cancer rates between the groups.
In addition, the incidence of breast cancer in the Swedish and Scottish studies was small, meaning the findings could have occurred due to chance.
Gale and Smith state categorically that Lantus and other insulins do not cause cancer. However, the European studies suggest that Lantus might promote more rapid growth of existing cancers, they say.
“We believe people are entitled to know that use of Lantus insulin might be associated with greater risk, but this must also be balanced against the possibility that we might be causing unnecessary alarm by raising these concerns,” said Gale and Smith.
The scientists recommend that, “a large combined analysis of the best available databases worldwide is the best way forward.”
They add that EASD and Sanofi-Aventis (the makers of Lantus) are pledged to carry this investigation forward until we have either confirmed these preliminary observations or, more hopefully, finally put them to rest.”
Meanwhile, Sanofi issued a statement saying the new data showed no conclusive link between Lantus and cancer. Sanofi shares fell $2.20, or 7% on the news.