An analysis of patients enrolled in a US health plan found no evidence that the insulin glargine (Lantus, Sanofi) increased cancer risk compared to human insulin (NPH), reports a study published online in ‘Diabetes Care’.

Concerns about the risk of cancer among users of the long-acting insulin analog glargine first arose in 2009 when Lars Hemkens from the Institute for Quality and Efficiency in Health Care, Cologne, Germany, and colleagues published data from a large German health-insurance database showing a positive association between cancer incidence and insulin.

Based upon such heightened concerns, investigators began examining other US and European databases to determine whether the signal was real.

In the current study John Buse and colleagues, from the University of North Carolina at Chapel Hill, explored how cancer incidence compared in patients with diabetes initiating treatment with the insulin glargine compared with those taking NPH insulin, a nonanalog form of insulin with similar indications and clinical effects.

The study population consisted of all patients with at least one diagnostic code for diabetes enrolled in a US health plan between January 2003 and December 2010.

To be eligible patients were required to have had a second prescription of the same insulin within 180 days and to be free of cancer.

In the study 22,936 patients initiated glargine treatments and 5,536 patients initiated NPH treatments.

The results show that the HR for breast cancer among patients initiating glargine was 1.07 [95% CI 0.65–1.75]; for prostate cancer was 1.19 [95% CI 0.73–1.94]); and for colon cancer was 0.89 [95% CI 0.49–1.60]).

The overall HR for any cancer was 1.12 [95% CI 0.95–1.32].

Among the few people using glargine or NPH for two years the HRs for breast cancer in glargine users was 0.67 [95% CI 0.18–2.54] and close to 1.0 for other cancers.

Prostate cancer proved the exception where 12-24 month use of glargine produced an HR of 2.66 [95% CI 0.65–10.9].

The interpretation of this result, wrote the authors, should take into consideration the unusually low incidence rate of prostate cancer in the NPH cohort.

“Based on previous studies and the substantial contribution of our study, we conclude that there does not seem to be an increased risk for cancer, including breast cancer, after initiation of glargine compared with NPH in patients with (mostly type 2) diabetes,” write the authors.

The authors caution that the evidence for longer term treatment with glargine beyond two years in their study was limited.

View article: http://ecancer.org/