GCC 1366: Anti-Proliferative Response to NeoAdjuvant AIs in Overweight and Obese Patients

More than three quarter of patients with breast cancer are treated by hormone pills called tamoxifen and aromatase inhibitors (AIs). AIs are drugs that stop female hormone production. This hormone production mostly happens in fat, muscle, and breast tissue in postmenopausal women. The female hormone estrogen is an important hormone for the growth of breast cancer cells. Anastrozole (Arimidex®) and Letrozole (Femara®) are AIs that are approved by the Food and Drug Administration (FDA). They have been used since 2005 to treat women with early stage breast cancer. When given before surgery (neoadjuvant), both anastrozole and letrozole have been shown to successfully shrink breast cancer tumors in most patients. In over 50% of patients, anastrozole and letrozole when given for about 4 months also helped to improve surgery outcomes. On top of that, whether or not a patient responds to anastrozole and letrozole before surgery can help the doctor decide whether that patient needs additional chemotherapy. One of the things may influence the level of hormone is body weight. It has been previously shown that postmenopausal women with higher body fat have higher level of female hormone as well as an increased risk of breast cancer. This is likely due to an increase in aromatase activity in the fatty tissue. However, at the current time AIs are used at the same doses in all women with breast cancer no matter whether they have different body weight. Currently, we do not know for certain whether the same doses of AIs work as well in patients with higher body fat compared to patients with less body fat. The purpose of this study is to see if women with higher body fat respond differently to AI treatment compared to women with lower body fat.