Does obesity change the effect of aromatase inhibitors (AIs) on estradiol, leptin, insulin, and IGF-1 serum levels in breast cancer patients?

Abstract

e11008 Background: The complexity of the relationship between obesity and breast cancer reflects important contributions of obesity-related factors in the adjuvant therapy. The efficacy of adjuvant AIs compared to tamoxifen is lower in obese postmenopausal women. Therefore, we aimed to identify whether the effect of AIs on estradiol, leptin, insulin, and IGF-1 serum levels with respect to the status of the obesity in breast cancer patients. Methods: A total of 34 postmenopausal breast cancer patients treated with adjuvant AIs were enrolled in the study. Pretreatment and 3 months after treatment body weight, height, waist-to-hip (WHR) ratio and body mass index (BMI) were recorded. Blood samples for serum estradiol, leptin, insulin and IGF-1 were drawn after 12 hour starvation and stored in – 70o before and 3 months after the onset of AI treatment. Results: Median age and BMI were 61 years (range 49-84) and 31 (range 22-43), respectively. 18 (%52.9) patients were treated with letrozole and 16 (%47.1) patients were treated with anastrazole. There was no change in the 3 months period in weight, BMI and WHR. Estradiol levels were decreased significantly between the baseline and the 3rd month (p<0.01). There was a slight increase in the leptin levels between the basal and 3rd month (p>0.05). No significant change was detected in insulin and IGF-1 levels in the follow-up period. In the multivariate regression model, there was no difference between the effect of letrozole and anastrazole on estradiol levels. Pretreatment BMI did not alter the effect of AIs on estradiol levels. The only factor related with the effect of the AIs is the pretreatment estradiol levels. Conclusions: This study shows that the suppression of estrogen in obese breast cancer patients with AIs at the standard doses may not be different from non-obese patients. Further researches may show us other mechanisms for the obesity-related factors to improve outcome with aromatase inhibition in obese breast cancer patients.