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04-10-2017 | Breast cancer | News

Long-term insulin glargine use may increase breast cancer risk

medwireNews: Long-term use of the long-acting insulin analog glargine is associated with an increased risk for breast cancer in women with type 2 diabetes compared with the intermediate-acting neutral protamine Hagedorn (NPH) insulin, observational study data show.

“Despite these findings, the benefits and risks of insulin glargine must be considered by drug regulatory agencies before any changes to clinical practice can be made,” stress Samy Suissa (Jewish General Hospital, Montreal, Quebec, Canada) and co-authors of the study.

The researchers analyzed data from the UK’s Clinical Practice Research Datalink for 22,395 women aged 40 years or older who received insulin glargine (n=9575), a second long-acting insulin, detemir (n=3271), or NPH (n=9549) treatment between 2002 and 2012.

During up to 12 years of follow up (mean 4.4 years), there were 321 incident breast cancer cases, corresponding to a crude incidence rate of 3.3 cases per 1000 person–years.

Women who received insulin glargine had a significant 1.44-fold increased risk for breast cancer compared with those who received NPH insulin, after adjustment for potential confounders such as age, excessive alcohol use, smoking status, BMI, glycated hemoglobin, diabetes duration, prior insulin use, comorbidity, and use of other medication.

But when the researchers looked at duration of treatment, they found that the increased breast cancer risk was only significant from 5 years after glargine initiation (HR=2.23).

They also report in the Journal of Clinical Oncology that the risk was only increased after more than 30 insulin glargine prescriptions had been received (HR=2.29).

By contrast, women who used insulin detemir had no increased breast cancer risk compared with NPH users, regardless of duration or prescription numbers.

However, Suissa et al caution: ”Given the fewer number of women and shorter duration of use as the result of its more recent introduction to the UK market, future studies are needed to further evaluate the relationship between long-term use of insulin detemir and breast cancer.”

By Laura Cowen

medwireNews is an independent medical news service provided by Springer Healthcare. © 2017 Springer Healthcare part of the Springer Nature group

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