A registry study affirmed that insulin glargine (Lantus) didn’t significantly raise cancer risk compared with "human" insulin….
John Buse, MD, PhD, of the University of North Carolina at Chapel Hill, and colleagues found that, new insulin glargine users had a nonsignificant 12% higher incidence of cancer compared with those starting human neutral protamine Hagedorn (NPH) insulin when followed about a year.
The results were likewise nonsignificant for breast, prostate, and colon cancers specifically, the group reported online in Diabetes Care.
The results had been presented at the American Diabetes Association meeting in 2012, along with several other observational studies affirming no elevated cancer risk with insulin glargine versus NPH or versus standard care without insulin, countering concerns raised by some research published in 2009 suggesting elevated risk, particularly for breast cancer.
"While our study contributes significantly to our evidence base for long-term effects, this evidence is very limited mainly based on actual dynamics in insulin prescribing," the group cautioned.
That limitation was because patients largely didn’t stay on their initial insulin for prolonged periods in the study, not because of insufficient follow-up time, they explained.
"While limiting our evidence base with respect to risk for cancer, this relative lack of empirically observed, long-term use also limits the hypothetical potential for negatively affecting public health," Buse and colleagues noted.
They examined insulin initiation in the Inovalon MORE registry of U.S. health plans among individuals without pre-existing cancer from 2003 through 2010.
That database included 43,306 initiating treatment with insulin glargine and 9,147 starting on NPH.
While some baseline characteristics differed between these groups, the overall cancer propensity score based on the differences came out even.
During an average 1.2 years of follow-up, for the main as-treated analysis in which patients were censored at the time of stopping, switching, or augmenting their initial insulin treatment the adjusted hazard ratios with insulin glargine versus NPH were:
- 1.07 for breast cancer (95% CI 0.65-1.75)
- 1.19 for prostate cancer (95% CI 0.73-1.94)
- 0.89 for colon cancer (95% CI 0.49-1.60)
Insulin use for 12 to 24 months was associated with a nonsignificant 2.66-fold elevated risk of prostate cancer, though the researchers cautioned that this "outlier result should be interpreted taking into account the absence of a monotonic pattern over duration of use and the small number and the unusually low incidence rate of prostate cancer in the NPH cohort."
While longer-term follow-up in the cohort was limited, women on insulin for more than 2 years weren’t more likely to develop breast cancer than those on NPH (HR 0.67, 95% CI 0.18-2.54).
The researchers cautioned that that comparison was based on just 14 incident breast cancers, calling their findings "reassuring, but further study of breast cancer risk with long-standing glargine use is necessary."
Sensitivity analyses largely came up with the same results as in the main analysis.
- Mention that, patients largely didn’t stay on their initial insulin for prolonged periods in the study.
- Patients initiating insulin glargine rather than NPH do not seem to be at an increased risk for cancer.