Insulin-like growth factor 1 (IGF1) and breast cancer risk

May 17, 2010

Women with high levels of a hormone, insulin-like growth factor 1 (IGF1), may have a higher risk of breast cancer, suggests an analysis of several studies.   Previous study results have been inconsistent, with some smaller prospective studies reporting a positive association between elevated levels of IGF1 and an increase in breast cancer risk while other studies have not.  The Endogenous Hormones and Breast Cancer Collaborative Group conducted a pooled analysis of individual data from 17 prospective studies and published results in Lancet Oncology.  Researchers found that higher levels of IGF1 were associated with increased breast cancer risk. This association did not differ by menopausal status, but was confined to a risk of estrogen receptor positive breast cancer.

Although the pooled analysis included data that were collected prospectively, the methods for measuring IGF1 were not standardized.  All 17 studies reported substantially varying concentrations of IGF1, reflecting differences in assay methods.  Whether there is a causal relationship between high levels of IGF1 and increased breast cancer risk remains to be seen.