Insulin glargine use and breast cancer: a systematic review and meta-analysis

Background: Insulin is widely used in the treatment of diabetes. There is an increasing concern regarding the association between insulin glargine use and breast cancer. Aim: To systematically review the literature on insulin glargine use and breast cancer risk. Methods: A systematic literature search on the relevant articles assessing insulin glargine use and breast cancer during the period from January 2008 to January 2018 was carried out. Studies on animals, human cell line, and humans, in English language that state the duration and dose of insulin glargine use, and the number of participants were retrieved from MEDLINE, Web Of Science, EMBASE, PubMed, and EBSCO, using the keywords insulin glargine, insulin Lantus, insulin analogs, breast neoplasia, and breast cancer. Results: Out of 311 articles, 34 manuscripts stand after duplication removal and applying the inclusion and exclusion criteria (twelve experimental studies, eight reviews, and fourteen human studies). The reviews’ results were inconclusive, human studies showed no relation of insulin glargine with breast cancer except at high dose and long duration of ≥ five years, and prior human insulin use, while the experimental studies showed a decreased breast cancer latency. Conclusion: There is no association between insulin glargine and breast cancer. Some of the studies showed an association with a long duration of high doses and prior human insulin use. Treating physicians may need to use insulin glargine as the basal insulin of choice before human insulin, although the dose and duration need to be taken into consideration. Real-world studies are needed.