Relationship among circulating tumor cells, CEA and overall survival in patients with metastatic colorectal cancer

We previously reported results of a prospective trial evaluating the significance of circulating tumor cells (CTCs) in patients with metastatic colorectal cancer (mCRC). This secondary analysis assessed the relationship of the CTC number with carcinoembryonic antigen (CEA) and overall survival. Patients with mCRC had CTCs measured at baseline and specific time points after the initiation of new therapy. Patients with a baseline CEA value >= 10 ng/ml and CEA measurements within +/- 30 days of the CTC collection were included. We included 217 patients with mCRC who had a CEA value of >= 10 ng/ml. Increased baseline CEA was associated with shorter survival (15.8 versus 20.7 months, P = 0.012). Among all patients with a baseline CEA value of >= 25 ng/ml, patients with low baseline CTCs (< 3, n = 99) had longer survival than those with high CTCs (>= 3, n = 58; 20.8 versus 11.7 months, P = 0.001). CTCs added prognostic information at the 3-5- and 6-12-week time points regardless of CEA. In a multivariate analysis, CTCs at baseline but not CEA independently predicted survival and both CTCs and CEA independently predicted survival at 6-12 weeks. This study demonstrates that both CEA and CTCs contribute prognostic information for patients with mCRC.