Abstract
Colorectal cancer (CRC) remains one of the leading causes of cancer-related death due to its high metastatic potential. This study aimed to investigate the detection and heterogeneity of circulating tumor cells (CTCs) and the microsatellite instability (MSI) status in advanced CRC patients prior to any systemic front-line treatment. Peripheral whole blood was obtained from 198 patients. CTCs were detected using double immunofluorescence and a real time-polymerase chain reaction assay; whereas MSI status was evaluated using fragment analysis. Median age of the patients was 66 years, 63.1% were males, 65.2% had a colon/sigmoid tumor location and 90.4% had a good performance status (PS). MSI-High status was detected in 4.9% of the patients; 33.3%, 56.1% and 8.6% patients had at least one detectable CEACAM5(+)/EpCAM(+), CEACAM5(+)/EpCAM(-) and CEACAM5(-)/EpCAM(+) CTC, respectively, and 9.1% of the patients had CEACAM5mRNA-positive CTCs. Following multivariate analysis, age, PS and MSI were confirmed as independent prognostic factors for decreased time to progression, whereas age, PS and CTC presence were confirmed as independent prognostic factors for decreased overall survival. In conclusion, our data support the use of CEACAM5 as a dynamic adverse prognostic CTC biomarker in patients with metastatic CRC and MSI-High is considered an unfavorable prognostic factor in metastatic CRC patient tumors.