Circulating endothelial cells and endothelial progenitors as predictive markers of clinical response to bevacizumab-based first-line treatment in advanced colorectal cancer patients

Patients and methods: The absolute numbers of CEPs, total CECs (tCECs) and their resting (rCECs) and activated subsets were evaluated by multiparameter flow cytometry in 40 mCRC patients at baseline and before the administration of the third and sixth course of a bevacizumab-based first-line treatment. Fifty healthy subjects were utilized as control. Results: The overall response rate was 80%, overall clinical benefit was 90% and median progression-free survival (PFS) was 13.8 months. In our patients, tCECs and rCECs were significantly increased compared with healthy subjects. The patients who achieved a radiological response showed, at baseline, a significant decrease of rCECs and a trend in decrease of tCECs in comparison with patients not achieving response. Finally, a baseline absolute number of tCEC and rCEC < 40 cells/ml was evidenced in patients with a longer PFS. No correlation was found regarding CEP. Conclusions: Our study suggests significant correlations between both tCEC and rCEC baseline levels and the antitumor efficacy of a bevacizumab-based combination therapy in mCRC patients, thus confirming that these biomarkers could be used in the clinical setting as an early predictor of tumor response.