Impact of body mass index on estradiol depletion by aromatase inhibitors in postmenopausal women with early breast cancer

Abstract

Background:Body mass index (BMI) has an impact on survival outcome in patients treated with aromatase inhibitors (AIs). Obesity is associated with an increased body aromatisation and may be a cause of insufficient estradiol depletion.Methods:Sixty-eight postmenopausal oestrogen receptor-positive patients with early breast cancer were prospectively included in this study. Follicle stimulating hormone (FSH), luteinizing hormone (LH) and estradiol were analysed immediately in the clinical routine lab and in a dedicated central lab before (T1) and 3 months after start with aromatase inhibitors (T2).Results:A total of 40 patients were normal or overweight (non-obese: BMI 18.5–29.9 kg m−2) and 28 were obese (BMI⩾30 kg m−2). Aromatase inhibitors significantly suppressed estradiol serum levels (T1: 19.5 pg ml−1, T2: 10.5 pg ml−1, P<0.01) and increased FSH serum levels (T1: 70.2 mIU ml−1, T2: 75.7 mIU ml−1, P<0.05). However, after 3 months of AI treatment, estradiol levels of obese patients were nonsignificantly higher compared with non-obese patients (12.5 pg ml−1 vs 9.0 pg ml−1, P=0.1). This difference was reflected by significantly lower FSH serum levels in obese compared with non-obese patients (65.5 mIU ml−1 vs 84.6 mIU ml−1, P<0.01). The significant effects of BMI on FSH serum levels could be detected both in the routine as well as in the dedicated central lab.Conclusion:Aromatase inhibitors are less efficient at suppressing estradiol serum levels in obese when compared with non-obese women.