Association between insulin glargine and risk of cancer: an updated and comprehensive systematic review and meta-analysis of observational studies

Previous meta-analyses have demonstrated conflicting results regarding the association between glargine and the risk of breast, prostatic, and colorectal cancer. Nevertheless, the relationship between glargine and other cancers remains unresolved. Additionally, nine observational studies have been published since the release of the earlier systematic review in 2016. Consequently, the objective of this study was to conduct a comprehensive meta-analysis with the aim of synthesizing the existing evidence and resolving the conflicting results observed in previous studies investigating the association between insulin glargine and the risk of cancer.

A comprehensive search of the online databases of PubMed, Scopus, Web of Science, and Google Scholar was conducted using relevant keywords up to April 2024. We included observational studies that investigated the association between insulin glargine and the risk of developing different types of cancer.

In total, 48 observational studies were included, with a combined sample size of 7,341,398 individuals. The age range of the participants was between 47.72 and 77.6 years. The results of the meta-analysis indicated a significantly positive association between insulin glargine and the risk of breast (Effect Size (ES): 1.28, 95% CI: 1.08, 1.52; p = 0.004) and prostatic (ES: 1.45, 95% CI: 1.03, 2.06; p = 0.036) cancer compared to other insulins. Conversely, the risk of developing liver cancer was found to be significantly reduced (ES: 0.57, 95% CI: 0.35, 0.94; p = 0.026) in patients who used glargine. There was no significant association between insulin glargine and the development of colorectal, lung, and pancreatic cancers.

In conclusion, this meta-analysis indicates that insulin glargine use is associated with an increased risk of breast and prostate cancer compared to other insulins. Conversely, the risk of liver cancer was significantly decreased. Nevertheless, the association between other long-acting insulins and other cancers requires further investigation.