Insulin Therapy and Breast Cancer Risk

Some observational studies have suggested an association between insulin therapy and cancer risk. Using a meta-analytical approach, the risk of breast cancer in diabetic patients treated with insulin was compared to the risk in diabetic patients treated with a non-insulin therapy (NIT). A systematic literature search was conducted in the PubMed database from inception to October 2017. Studies with a prospective design including nested case-control and case-cohort studies were selected. Summary relative risks (SRR) of breast cancer associated with the use of any type of insulin therapy compared to NIT were computed using a random-effect model. Three sub-analyses were carried out: one according to the adoption of a new-user design (i.e., including only new users of a drug) vs. a prevalent user design (i.e., including both new and past users of a drug); one according to the type of comparator (specific NIT vs. any type of NITs); and one according to the type of diabetes. A total of 12 studies, representing 1,392,040 diabetics and 15,430 breast cancer cases, were included in the analysis. Overall, the SRR of breast cancer associated with insulin use was 0.97 (95% CI: 0.87, 1.08) with a high degree of heterogeneity between studies (I²=60%, p Disclosure C. Pizot: None. M. Dragomir: None. P. Boyle: Other Relationship; Self; Sanofi. P. Autier: Other Relationship; Self; Sanofi.