When stratified by levels of insulin and the IGF axis biomarkers, participants with low insulin (HR: 1.42; 95% CI: 1.11–1.82), low C-peptide (HR: 1.41; 95% CI: 1.10–1.80), and low IGF1/IGFBP3 ratio (HR: 2.55; 95% CI: 1.18–5.49) exhibited increased risk of breast cancer recurrence (Table 3). This evidence concerns the gene IGF1 and breast cancer.