Abstract P1-12-04: Long Term Follow-Up of a Pilot Trial of Pre-Operative (Neoadjuvant) Letrozole in Combination with Bevacizumab in Post-Menopausal Women with Newly Diagnosed Estrogen and/or Progesterone Receptor Positive Breast Cancer

Abstract

Introduction: Overexpression of vascular endothelial growth factor (VEGF) in breast cancer tumors has been associated with resistance to anti-estrogen adjuvant therapy. We designed a pilot study of neoadjuvant letrozole and bevacizumab (anti-VEGF) to assess feasibility and short term efficacy in post-menopausal women with stage II/III, ER/PR positive breast cancer. Patients and Methods: Patients were treated with a neoadjuvant regimen of letrozole, 2.5 mg/day (PO) and bevacizumab 15 mg/kg every 3 weeks (IV) for a total of 24 weeks prior to surgical treatment of their breast cancer. Patients were followed for toxicity at three week intervals and tumor assessment (physical exam and tumor ultrasound) at six week intervals. Results: Twenty-five evaluable patients were treated. The regimen was well tolerated except for two patients who were taken off-study for difficult to control hypertension. Objective clinical response occurred in 17/25 patients (68%) including 16% CR and 52% PR. The four patients with clinical CR had pathologic CR in their breasts (16%) although one had residual tumor cells in axillary nodes. Two of the 17 responding patients were lost to follow-up; with a median follow-up of 50 months, no relapses have been seen in the 15 responsive patients, including 10 patients who received no adjuvant chemotherapy. Two patients with progressive disease at 9 and 16 weeks received neoadjuvant chemotherapy, surgery and radiation. One of these patients relapsed at 35 months and the other is NED at 44 months. Four patients had stable disease and all received adjuvant chemotherapy; one patient relapsed at 25 months, and the reminder are NED at 44-52 months. Overall, 2 out of 21 patients with adequate follow-up had disease reoccurrence (9.5%) at a median follow-up of 45 months. Conclusion: Combination neoadjuvant therapy with letrozole and bevacizumab was well tolerated and resulted in impressive clinical and pathologic responses. Data suggest that patients having an objective response to neoadjuvant therapy had excellent 4 year disease-free survival (100%) while relapsed occurred in 2 out of 6 patients who failed to have an objective response despite additional neoadjuvant or adjuvant chemotherapy. The Breast Cancer Translational Research Consortium has an ongoing randomized phase II trial of letrozole ± bevacizumab in this patient population. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-12-04.