Deleterious Effect of Chemotherapy on Measures of Insulin Resistance in Patients with Newly-Diagnosed Invasive Breast Cancer.

Abstract

Abstract Background: Women treated with early stage breast cancer often gain weight in the two years following diagnosis, with adjuvant chemotherapy, younger age, lower body mass index (BMI) and pretreatment menopausal status being associated factors (Breast J 2007; 13:258). The effect of insulin resistance on treatment-related weight gain, and of treatment on measures of insulin resistance, are unclear.Purpose: To prospectively study weight gain in women receiving adjuvant therapy for early stage breast cancer and assess changes in body mass index, body composition, and explore the relationship between markers of insulin resistance, cancer therapy, exercise and weight gain.Methods: Prospective, observational study of non-diabetic women with early-stage breast cancer receiving adjuvant chemotherapy and/or hormonal therapy. Fasting insulin, glucose, and triglycerides, weight, BMI, waist and hip circumference were obtained at baseline before adjuvant therapy, and at 6, and 12 months. Patients completed nutrition and exercise logs using the Nutritionist-Pro program. Insulin resistance was calculated using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Waist/hip ratio (WHR) was used as a surrogate for percent body fat.Results: Complete data available for 95 patients are reported regarding weight change at 6 months (mean 0.4 kg, 95%CI -0.3, 1.0; p=.23 compared to baseline) and 12 months (0.9 kg, 95%CI 0.4, 1.8, p=.04 compared with baseline). Mean baseline HOMA-IR was 2.3 (95%CI 1.9, 2.7); mean baseline WHR was 0.82 (95%CI 0.81, 0.84). Six-month HOMA-IR tended to increase (by mean 0.34, p=.06) as did glucose/insulin ratio (p=.05). Waist measurement (p=.96) and WHR (p=.52) were unchanged. Chemotherapy-treated patients exhibited adverse changes compared with others (mean change for chemotherapy-treated and no chemotherapy for HOMA-IR: 0.53 vs. -0.64, p=.005; glucose/insulin: -2.1 vs. 2.7, p=.003; waist: 0.37 vs. -1.94 cm, p=.08; WHR: 0.001 vs. -0.024, p=.06). Age, BMI, hormonal therapy, or types of breast surgery were not associated with significant changes. Exercising patients demonstrated lower HOMA-IR and WHR, and greater glucose/insulin ratios at baseline, but exercise (aerobic, strength, or any exercise) was not associated with significant change at 6 and 12 months for any of these variables. While differences disappeared at 12 months despite further weight gain repeated measures analysis of variance confirmed the effect of chemotherapy over time for HOMA-IR (p=.048), glucose/insulin (p=.038) and WHR (p=.050).Conclusions: These preliminary data suggest that patients completing chemotherapy within 6 months of baseline appear to experience at least short-term changes in metabolism suggestive of insulin resistance. These adverse changes may help explain weight gain associated with adjuvant chemotherapy, and merit further prospective study. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1054.