A pilot open-label trial of preoperative (neoadjuvant) letrozole in combination with bevacizumab in postmenopausal women with newly diagnosed operable breast cancer

625 Background: Preclinical studies suggest that up-regulation of tumor cell VEGF is a mechanism to subvert estrogen dependence in hormone responsive breast cancer resulting in reduced efficacy or acquired resistance; we hypothesized that the combination of bevacizumab (an anti-VEGF MoAb) and hormone therapy would be more effective than hormone therapy alone for the treatment of breast cancer. Methods: Postmenopausal, ER and/or PR positive and Her-2-neu negative, operable (T2–4a-c/N 0–2/M0) breast cancer patients were enrolled. Patients received letrozole (2.5 mg po daily) and bevacizumab (15 mg/kg IV q 3 wks). Patients were evaluated every 6 wks; patients with CR/PR/SD in the first evaluation continued; after an additional 6 weeks of therapy patients with PD or SD were taken off-study and those patients with PR/CR completed 24 weeks of therapy. Definitive surgery was performed no sooner than 4 wks after the last dose of bevacizumab. Patients continued letrozole while waiting for surgery. 26 patients were...