Analysis of Circulating Tumor DNA to Monitor Metastatic Colorectal Cancer Treatment

Colorectal cancer (CRC) is the third of the most common cancers and the second leading cause of cancer death in western countries. CRC is diagnosed at metastatic stage in approximately 35% of cases, while about 20% to 50% of patients diagnosed at earlier stage (stage II and III) will develop distant metastasis subsequently. Treatment efficacy is usually evaluated by computer tomography (CT) scan with RECIST criteria and dosage of carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9, which were performed every two weeks during the chemotherapy. The management of treatment for metastatic CRC need the development of early biomarkers to evaluate the efficacy in order to avoid unnecessary toxicity in case of early chemotherapy resistance. In this prospective study, the investigators will compare the monitoring of circulating tumor DNA with the results of CT scan according the RECIST criteria and the blood level of CEA and CA 19-9. The investigators carried out a microfluidic digital polymerase-chain-reaction (PCR) assay to measure the specific somatic genomic alterations in plasma to identify the circulating tumor DNA.