Objective Several studies have been published in 2009 suggesting a possible association between insulin glargine and increased risk of malignancies, including breast cancer. The objective of this study was to assess the relation between the individual insulins (glargine, aspart, lispro and human insulin) and development of breast cancer.
Research Design and Methods 775 incident cases of primary invasive or in situ carcinoma breast cancer occurring in women with diabetes from 92 centers in the U.K., Canada and France were matched to a mean of 3.9 diabetic community controls (n=3050; recruited from 580 general practices) by country, age, recruitment date, diabetes type and management. The main risk model was a multivariate conditional logistic regression model with case/control status as the dependent variable and individual insulin use, 8 years preceding the index date, as the independent variable, controlling for past use of any insulin, oral anti-diabetic drugs, reproductive factors, lifestyle, education, hormone replacement therapy and history of contraceptive use, BMI, comorbidities, diabetes duration, and annual number of physician visits. Glargine was also compared to every other insulin by computing all ratios using the variance-covariance matrix of logistic model parameters.
Results Adjusted odds ratios of breast cancer for each type of insulin vs. no use of that insulin were: 1.04 [95% CI 0.76-1.44] for glargine; 1.23 [0.79-1.92] for lispro; 0.95 [0.64-1.40] for aspart; and 0.81 [0.55-1.20] for human insulin. Two-by-two comparisons found no difference between glargine and the different types of insulins. Insulin dosage or duration of use and tumor stage did not change the results.
Conclusions This international study found no difference in the risk of developing breast cancer in patients with diabetes among the different types of insulin with short- to mid-term duration of use. Longer term studies would be of interest.
- Received March 22, 2013.
- Accepted August 9, 2013.
- © 2013 by the American Diabetes Association.
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