Circulating endothelial cells (CECs) in metastatic colorectal cancer (mCRC) patients (pts) treated with bevacizumab (BEV) and sorafenib.

e14063 Background: Surrogate biomarkers are lacking for predicting or monitoring anti-angiogenesis therapies. We investigated if CECs were correlated to treatment efficacy in mCRC pts treated with BEV and sorafenib. Methods: Peripheral blood samples were obtained for CEC analysis from mCRC pts enrolled in the NCCTG phase II study N054C [Grothey, ASCO 2010]. Blood collection time points were: baseline (BL), cycle 1 day 3, prior to treatment cycles 2, 3, 5, 7, 9, 11, 13, and after the pt went off study. CECs, defined as CD146(+), CD3(-), and CD31(+), were enumerated by flow cytometry. Unequal variance two-sample and paired t-tests were performed to compare values between pt outcome groups and serial measurements within a pt, respectively. Results: 78/79 eligible N054C pts went off study and had their CECs analyzed. 76 pts had BL blood evaluable for CEC analysis. Median BL CECs were 80.0 (mean: 177.5; range: 1.02-1718) cells/mL. We found no correlation between BL CECs and 3 month progression-free survival fo...