Relation between Insulin Resistance and Breast Cancer among Chilean Women

Purpose In Chile, diabetes and breast cancer are important public health problems. The association between insulin resistance and breast cancer, however, remains largely unexplored. Methods We conducted a case-control study to assess the relationship of insulin resistance (IR) and breast cancer in Chilean premenopausal and postmenopausal women. We compared 170 women, 33 to 86 years old, with incident breast cancer and 170 normal mammography controls, matched by 5-year age interval. Plasmatic insulin and glucose were measured and IR was calculated by the homeostasis model assessment method. Anthropometric measurements and sociodemographic and behavioral data were also collected. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by multivariable conditional logistic regression. Results IR was independently associated with breast cancer in postmenopausal women (OR = 2.70, 95%CI = 1.10–6.63), but not in premenopausal women (OR = 0.84, 95%CI = 0.20–3.52). Obesity was not associated with breast cancer at any age (OR = 0.68, 95%CI = 0.39–1.20). Conclusion In this sample, IR increased the risk of breast cancer among postmenopausal women.