Use of circulating endothelial cells to predict response to FOLFOX4 plus bevacizumab in metastatic colorectal cancer.
427 Background: The purpose of this study was to identify CEC threshold proposal for determining response to FOLFOX4 plus bevacizumab in metastatic colorectal cancer (mCRC). Methods: All patients were enrolled using institutional review board-approved protocols at the Cancer Institute Hospital and provided informed consent. From July 2007 to June 2008, 33 patients treated with FOLFOX4 plus bevacizumab were enrolled in a prospective study. From January 2007 to June 2007, before bevacizumab was approved by the government in Japan, 31 patients treated with FOLFOX4 as a control were enrolled. The study population consisted of patients aged 18 years or older with histologically proven mCRC. Other inclusion criteria were Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, adequate organ function. CECs of whole blood at the baseline, day 4, 2 weeks after initiation of chemotherapy were isolated and counted using immunomagnetics. Results: There was no correlation between CEC levels and the outcome in the FOLFOX4. In the FOLFOX4 plus bevacizumab, CEC levels at the baseline were significantly associated with the outcome. Patients with 65 or more CECs at the baseline had shorter median PFS (9.2 months), than the median PFS of fewer than 65 CECs at the baseline (18.9 months) in the FOLFOX4 plus bevacizumab (p = 0.003). Patients with 65 or more CECs at the baseline had shorter median OS (23.3 months), than the median OS of fewer than 65 CEC s at the baseline in the FOLFOX4 plus bevacizumab (p = 0.027). In the univariate analysis, lung metastasis, lymph node metastasis, and CEC levels at the baseline predicted PFS. In the univariate Cox regression analyses, peritoneal metastasis, CEC levels at the baseline were associated with OS. In order to evaluate the independent predictive effect of FOLFOX4 plus bevacizumab, multivariate Cox regression analysis was carried out. CEC levels at the baseline were the strongest predictor. Conclusions: A threshold of lower than 65 CEC/4mL at the baseline was a significant predictor of the outcome for colorectal cancer patients treated with FOLFOX4 plus bevacizumab. No significant financial relationships to disclose.