IGF1 and breast cancer: A large meta‐analysis examining the effects of circulating IGF1 and IGFBP3 levels on the risk of developing several common cancers detected an association between increased IGF1 concentration and prostate, colorectal and pre‐menopausal breast cancer risk, while perhaps surprisingly, increased IGFBP3 levels were associated with risk of pre‐menopausal breast cancer.