Three major studies examining long-acting insulin use in the U.S. and Europe found no increased risk of a wide range of cancers in patients using glargine, contradicting previous suggestions that there may be a link, researchers reported at the American Diabetes Association’s 72nd Scientific Sessions®.
Researchers in five northern European countries (Norway, Sweden, Denmark, Finland and Scotland), at the Kaiser Permanente in Northern and Southern California, and at the University of North Carolina (using MedAssurant U.S. healthcare insurance databases and electronic medical records from Louisiana and Massachusetts) independently compared use of long-acting insulin glargine (trade name Lantus) for patients with diabetes with other long-acting insulins and found no increased risk of a wide range of cancers.
“The preponderance of the evidence suggests that there is no increased risk of cancer associated with relatively short-term use insulin,” said John Buse, MD, PhD, director of the Diabetes Center at the University of North Carolina School of Medicine. A series of previous studies, published in 2009, had suggested a possible link between use of glargine and an increased risk of cancer, with conflicting results.
Researchers at all locations looked at the association between insulin use and all cancers, as well as at the individual risks for breast, colorectal and prostate cancers. Only one study, by researchers in the Kaiser Permanente group, found a “suggestion” of an association between insulin glargine use and a modest increase in breast cancer risk, but only among new insulin users. They found no association with prostate, colorectal cancer or all cancers combined in new users or in prior users of insulin. Principal Investigator Laurel Habel, PhD, Research Scientist at the Kaiser Permanente Northern California Division of Research, noted that “results of their study should be viewed cautiously, given the relatively short duration of glargine use and the large number of associations examined. Further, because the induction period for many carcinogens is years to decades, additional follow-up of the Kaiser cohort and others will be needed to determine whether glargine is associated with an increase in breast, or other forms of, cancer.”
The Kaiser Permanente group examined data for 115,000 patients with diabetes who were taking either insulin glargine or another commonly used long-acting insulin known as NPH. They compared cancer risk in new insulin users as well as patients who had switched from NPH to glargine. There was a median duration of 1.2 years for glargine use and 1.4 years for NPH.
None of the other groups found any association between glargine use and an increased risk of breast cancer or any other type of cancer.
Researchers at the University of North Carolina used a large, automated healthcare database (MedAssurant) to identify 43,306 patients initiating glargine and 9,147 initiating NPH, all of whom were free of cancer when they initiated insulin use. The mean duration of treatment was 1.2 years for the glargine group and 1.1 years for those taking NPH. Follow-up was discontinued when a patient experienced a change in their insulin treatment.
“In conclusion we found no evidence of an increased risk for cancer and we specifically found no increased risk for breast cancer in the small group that stayed on these drugs for more than 24 months,” said Principal Investigator Til Stürmer, MD, MPH, PhD, Professor of Epidemiology and Director of the Center of Excellence in Pharmacoepidemiology and Public Health, University of North Carolina Gillings School of Global Public Health. “Our study adds to the important evidence about long-term outcomes of these antidiabetic treatments.”
The Northern European Study of Insulin and Cancer is the largest study of its kind comprising 447,821 diabetic patients using insulin, over 1.5 million person-years of observation and 17,500 new cases of cancer in the cohorts. The average follow-up time is longer than any other follow-up study, at 3.1 years for those on glargine and 3.5 years for other insulins. This study looked at the risk for all cancers, as well as individually for breast, lung, pancreas, colorectal and prostate cancers.
“There was no difference in risk between glargine and other insulins found in any of the pre-defined primary and secondary hypotheses of this study,” said Principal Investigator Peter Boyle, PhD, President of the International Prevention Research Institute in Lyon, France.
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