Circulating tumor cell (CTC) count and epithelial growth factor receptor expression on CTCs as biomarkers for cetuximab efficacy in advanced colorectal cancer.

BACKGROUND/AIM The purpose of this study was to establish whether CTC count and epidermal growth factor receptor (EGFR) expression in CTCs predicted outcome in patients with advance colorectal cancer (ACC) receiving cetuximab as third-line treatment. PATIENTS AND METHODS Between October 2008 and March 2011, 63 patients with KRAS wild-type ACC were treated with cetuximab-containing chemotherapy at the Cancer Institute Hospital. We measured the CTC count and EGFR expression on CTCs using the CellSearch System (Veridex LLC, NJ, USA). RESULTS Nineteen patients (30%) with a high number of CTCs had a significantly lower overall survival compared with 44 patients with a low number of CTCs. No significant difference was observed in progression-free survival between the two groups. Out of the 33 patients positive for CTCs (one or more CTC), seven patients (21%) were positive for EGFR expression. No statistically significant difference was observed in clinical outcome between EGFR-positive and EGFR-negative patients. CONCLUSION A high CTC count predicted reduced overall survival in patients with ACC treated with cetuximab-combination chemotherapy as third-line treatment. These results suggest that the assessment of CTCs might provide with important prognostic information for such patients.