Circulating tumour cells early predict progression-free and overall survival in advanced colorectal cancer patients treated with chemotherapy and targeted agents

Background: Early predictive markers for response are needed for advanced colorectal cancer (ACC) patients. We assessed the value of circulating tumour cells (CTC) in ACC patients treated with chemotherapy plus targeted agents (CAIRO2 phase III trial) and compared the results with computed tomography (CT) imaging. Materials and methods: CTC were determined at baseline and at different time points during treatment. Patients were stratified into low (less than three CTC per 7.5 ml of blood) or high CTC (three or more CTC per 7.5 ml of blood). Results: A total of 467 patients were assessable for CTC analysis. Among them, 129 patients (29%) with high baseline CTC had a significantly decreased progression-free survival [PFS; hazard ratio (HR) 1.5] and overall survival (OS; HR 2.2) compared with 322 patients with low baseline CTC. This difference remained statistically significant during treatment. The sensitivity and specificity of high CTC at baseline for the prediction of progressive disease on CT imaging were 16.7% and 70.1%, respectively, and of high CTC at 1-2 weeks after the start of treatment 20.0% and 95.1%, respectively. The combined analysis of CTC and CT imaging provided a more accurate outcome assessment than either modality alone. Conclusions: The CTC count before and during treatment independently predicts PFS and OS in ACC patients treated with chemotherapy plus targeted agents and provides additional information to CT imaging.