Circulating biomarkers in patients receiving neoadjuvant chemotherapy combined with sunitinib for locally advanced breast cancer.

1089 Background: Biomarkers to guide the use of antiangiogenic therapy are lacking. Circulating endothelial cells (CECs) and their progenitor cells (CEPs) are increased in cancer patients. VCAM is an endothelial protein increased in response to VEGF stimulation, while CAIX is elevated in states of hypoxia; both correlate with tumor aggressiveness. Methods: We examined these circulating biomarkers in a phase II neoadjuvant trial in 63 patients (pts) with locally advanced HER2 negative breast cancer treated with 12 weeks (wks) of paclitaxel (T) plus sunitinib (S) followed by 15 wks of daily oral cyclophosphamide and weekly doxorubicin plus daily G-CSF (AC+G-CSF). Toxicity and clinical outcomes are reported as a separate abstract. Blood was collected at baseline, wk 12 and pre-surgery. For this analysis, responders were defined as patients with a pathologic complete response (pCR) and/or MDACC CPS+EG score ≤ 2 (a validated score combining clinical and pathologic results for predicting survival in the neoadju...