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Background: Studies on the association between circulating insulin-like growth factor 1 (IGF1) and prognosis of breast cancer are limited. Whether this association is modified by insulin levels and clinical characteristics is unclear. Methods: Serum concentrations of IGF1 as well as IGF binding protein 3 (IGFBP3), IGF1/IGFBP3 ratio, insulin, and C-peptide were prospectively examined in 2,682 invasive breast cancer patients who received surgery in Ruijin Hospital, Shanghai, between 2012 and 2017. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality, breast cancer-specific mortality, and breast cancer recurrence associated with different levels of IGF1 and other biomarkers with multivariable adjustment. Results: Compared with patients with low IGF1, patients with high IGF1 had a significantly lower risk of all-cause mortality (HR, 0.53; 95% CI, 0.29–0.96) and a borderline lower risk of breast cancer-specific mortality (HR, 0.53; 95% CI, 0.27–1.02). The inverse association between IGF1 and all-cause mortality was consistent across stratification subgroups but was more pronounced among patients with high insulin (HR, 0.40; 95% CI, 0.18–0.89), were premenopausal (HR, 0.34; 95% CI, 0.12–0.97), with a tumor size >2 cm (HR, 0.35; 95% CI, 0.17–0.73), with positive lymph node (HR, 0.49; 95% CI, 0.25–0.98), and with a high Ki-67 level (HR, 0.49; 95% CI, 0.26–0.95) (all P for interaction >0.05). No significant associations were found for IGFBP3, IGF1/IGFBP3 ratio, insulin, and C-peptide levels with all-cause mortality, breast cancer-specific mortality, and breast cancer recurrence. Conclusion: Circulating IGF1 was inversely and independently associated with all-cause mortality in invasive breast cancer patients, and this association was consistent across clinical risk factors. [ABSTRACT FROM AUTHOR]

Background: The interplay between biomarkers of insulin and the insulin-like growth factor (IGF) axis in the context of breast cancer risk is unclear. Methods: We measured the concentrations of insulin, C-peptide, IGF1, and IGF binding protein 3 (IGFBP3) and calculated the homeostasis model assessment of insulin resistance (HOMA-IR) index and the IGF1/IGFBP3 ratio among 2536 patients with breast cancer and 2528 patients with benign breast disease recruited from Ruijin Hospital, Shanghai, China, between 2012 and 2017. Results: Multivariable-adjusted odds ratios (ORs) for breast cancer associated with the highest quartiles versus the lowest quartiles of insulin and IGF factors were 1.45 (95% CI, 1.20– 1.75) for insulin, 1.32 (1.08– 1.60) for C-peptide, 1.53 (1.26– 1.85) for HOMA-IR, and 1.27 (1.05– 1.53) for IGF1; these associations did not differ substantially across stratifications of age, body mass index, age at menarche, or menopausal status (all P for interaction > 0.05). In the joint analysis, the highest quartile of IGF1 was associated with the greatest risk of breast cancer in the highest quartiles of insulin (OR, 1.77; 95% CI, 1.29– 2.44), C-peptide (1.60; 1.17– 2.20), and HOMA-IR (1.90; 1.38– 2.62), compared with the risks associated with the combination of the lowest quartiles of IGF1 and each insulin factor. In stratification analysis, the positive association between IGF1 and breast cancer was stronger in the highest quartiles of insulin (P[interaction] = 0.29), C-peptide (P[interaction] = 0.020), and HOMA-IR (P[interaction] = 0.075). Conclusion: Our findings indicate effect modifications of insulin, C-peptide, and insulin resistance on the relationship between IGF1 and breast cancer risk in Chinese women. [ABSTRACT FROM AUTHOR]