Changes in glucose, insulin, and insulin resistance from presurgery to post adjuvant treatment for breast cancer.

Abstract

1511 Background: Elevated fasting insulin levels at breast cancer diagnosis are associated with increased risk of recurrence and reduced survival. (Goodwin PJ, et al. JCO. 2012;30:164-171) Weight gain related to adjuvant treatment coupled with sedentary activity habits may further alter insulin-related measures for breast cancer survivors. We present results from a prospective longitudinal study examining changes in insulin-related markers from pre breast cancer surgery to post adjuvant treatment. Methods: Subjects were recruited from St. James’s hospital, Dublin, Ireland at the time of breast cancer diagnosis (stage I-III). Fasting pre-surgery blood samples were drawn to measure insulin, glucose and glycosylated haemoglobin A1c (HBA1C). Insulin resistance was calculated using the homeostatic model assessment (HOMA). Subjects with no evidence of active cancer completed the same measurements 2-5 years later. Paired sample t-tests were used to measure changes from pre-surgery to post-adjuvant treatment. Statistical significance was set at P = .05. Results: Forty-four subjects (n = 22 postmenopausal) completed both measurements (mean ± SD age 54.1±8.6 years). Mean time since diagnosis to follow-up measures was 3.4±0.8 years. Adjuvant therapy included chemotherapy (n=37), radiotherapy (n=36), biological therapy (n=8) and concurrent hormonal therapy (n=37). There was a statistically significant increase in insulin (mean ± SD change 2.8±4.1mU/L, P=.000), insulin resistance (0.54±1.0, P=.001) and HBA1C (0.1±0.2 %, P= .003). Fasting glucose levels did not change (P = .06). Conclusions: Results indicate that patients with breast cancer experience significant increases in insulin, insulin resistance and HBA1C from pre-surgery to post adjuvant treatment. Elevated post-treatment insulin levels may further contribute to risk of breast cancer recurrence and mortality, while also predisposing to the development of cardiovascular disease and type 2 diabetes mellitus. Exercise and diet interventions are warranted in this population to improve markers of insulin resistance as a surrogate for improving breast cancer and overall health outcomes.