Circulating tumor DNA (ctDNA) are small fragments of nucleic acid that originate from apoptotic or necrotic tumor cell turnover. Characteristic of the malignant process, ctDNA can be assessed in plasma and offers the potential of a sensitive and specific biomarker for prognostic information on disease-free or overall survival, and predictive information on chemotherapy resistance and probability of lack of response to treatment. This study will evaluate ctDNA as a prognostic marker and as a monitor of disease recurrence in stage III colorectal cancer (CRC). We will recruit newly diagnosed stage III CRC patients, determine their tumor mutational profile, and systematically collect high volume (\>10 ml), serial plasma specimens every 3 months for up to 3 years and every 6 months in years 4-5 for ctDNA and concurrent carcinoembryonic antigen (CEA) measurement. Clinical outcome and survival will be tracked. The resulting data will permit assessment of ctDNA as a prognostic marker for disease-free and overall survival and as a monitor of disease recurrence in comparison with CEA.
