This study is to evaluate circulating tumor DNA (ctDNA) as a predictive and surveillant method for tumor recurrence in stage II and III colorectal cancer (CRC).

This study will evaluate circulating tumor DNA (ctDNA) as a prognostic marker and as a monitor of a short-term disease recurrence in surgical resective stage II and stage III colorectal cancer (CRC). The investigators will recruit newly diagnosed CRC patients, systematically collect their blood samples at the following time point: before surgery, one week after surgery, every three months for the first year and every six months for the second year, which are coincidence with the recommended clinical follow-up. Patients' outcome and survival will be tracked. These study will permit assessment of ctDNA as a predictive and surveillant method for a short-term (two years) tumor recurrence in comparison with other parameters.

Inclusion Criteria:

• Male or female ≥ 18 years of age on the day of signing informed consent.
• Patients must have histologically confirmed stage II or IIIcolorectal cancer.
• Patients must receive radical resection.
• Written informed consent must be obtained from patient or patient's legal representative and ability for patient to comply with the requirements of the study.

Exclusion Criteria:

• Patient has severe anemia.
• Patients received neoadjuvant treatment.
• Patients received blood transfusion two weeks before or during the surgical resection.
• Patient has any other conditions, which, in the opinion of the Investigator, would interfere with the evaluation of the subject

Patients with stage II or stage III colorectal cancer must have baseline evaluations performed prior to the study and must meet all inclusion and exclusion criteria.