Both Health Canada and the FDA are undertaking a safety review of insulin glargine (trade name is Lantus ©), in response to four studies that were published in this month’s Diabetologia journal. Three of these four European observational studies suggested that there may be higher rates of cancer amongst patients who use Lantus insulin.
Lantus is one of two long acting synthetic insulins (the other is insulin detemir, trade name Levemir ©). Levemir © was not studied in the above mentioned studies, because it is a newer insulin that was not available at that time. These insulins have been altered from long acting human insulin (known as N or NPH insulin), resulting in different actions of these insulins, with benefits including a longer duration of action and lower risk of low blood sugars (hypoglycemia) compared to human insulin.
Some studies have suggested an increased risk of cancer in all patients with diabetes (on any kind of treatment), though the common denominator here may be obesity (obesity is a well known risk factor for several types of cancers). People with type 2 diabetes (particularly in the earlier years) and people who are overweight or obese often have high insulin levels, also known as insulin resistance. Insulin is an important growth factor, for example for cells that line the colon; in fact, insulin has been shown to stimulate colonic tumor cells. So, insulin in general, whether produced internally, or given as a treatment of diabetes, may be associated with an increased risk of cancer.
So how does Lantus © play into all of this? Lantus © is known to interact with insulin growth factor receptors to a higher degree than other insulins, which could theoretically be associated with increased cancer risk. However, it has to be taken into consideration that these recent studies were observational only, and therefore not high quality data (in other words, not something we can hang our hat on).
The bottom line is, that we do not know at this time whether Lantus © increases cancer risk. Health Canada and the FDA are doing the right thing by looking into this issue. In the meantime, it is important not to take extreme reaction to information that is highly debatable. If you are taking Lantus ©, it is important that you do not simply stop taking it, as not treating your diabetes can lead to dangerously high blood sugars. If you are concerned, please speak to your doctor about the issue, and make a decision about your diabetes treatment that is best for you.