Abstract 373: Circulating endothelial cell measurement allows early prediction of outcome in patients with metastatic colorectal cancer treated with first-line bevacizumab and chemotherapy. Findings from the FNCLCC ACCORD 13/0503 randomized phase II trial

Abstract

Abstract Purpose - There is no validated biomarker to predict the efficacy of bevacizumab. We tested the hypothesis that circulating endothelial cells (CEC) levels could predict clinical outcome of metastatic colorectal cancer (mCRC) patients starting treatment with bevacizumab and chemotherapy. Patients and Methods - Among the 145 mCRC patients treated with first-line bevacizumab and irinotecan-based chemotherapy (either FOLFIRI or XELIRI regimen) in the FNCLCC ACCORD 13/0503 randomized phase II trial, 99 agreed to blood sampling at day [D]1 (before treatment) and D15 or 22 (at the end of cycle 1). CEC (CD45-CD31+CD146+7-amino-actinomycin- cells) were quantified by four-color flow cytometry according to a previously validated method. We assessed whether D1 or D15/22 CEC levels, or changes in CEC levels between D1 and D15/22, correlated with patient characteristics, 6-month objective response rate (ORR), and 6-month progression-free survival (PFS) rate (the trial primary endpoint). Results - CEC levels were higher at D1 in patients with altered PS (p=0.02). CEC levels were higher at D15/22 in the absence of objective response (p=0.04), and at D1 (p=0.01) and D15/22 (p=0.03) in patients whose disease progressed within 6 months of treatment. The best outcome (6-month PFS rate, 96%) was observed in patients with low CEC levels at D1 and D15/22 (cutoff, baseline median=16/mL) compared to patients with high CEC levels at either D1 or D15/22 (79%) and patients with high CEC levels at D1 and D15/22 (68%; trend test, p=0.01). Conclusions - CEC levels may help in early prediction of efficacy of first-line bevacizumab and chemotherapy in mCRC patients. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 373.