Does Obesity Attenuate Aromatase Inhibition?

Obesity is associated with elevated levels of circulating estrogen because steroid precursors are converted to estradiol by aromatase enzymes in adipose tissue. Estrogen exposure is a well-known risk factor for developing breast cancer, and obese women with early stage breast cancer (in particular, those with body-mass index ≥35 kg/m²) who receive the aromatase inhibitor anastrozole may have greater risk for disease recurrence than women who are of normal weight or who receive tamoxifen. These findings raise concerns that aromatase inhibition as a risk-reduction strategy might be less effective in obese women, and that use of less-potent aromatase inhibitors such as anastrozole might adversely affect clinical outcome. Evidence suggesting th…