In this study, we aim to investigate the value of circulating tumor DNA (ctDNA) analysis in the diagnosis, treatment, and surveillance of patients with surgically resectable colorectal cancer, by performing serial analysis of ctDNA, next-generation sequencing of surgical specimens, and observation of patients undergoing radical resection of the tumor with or without adjuvant chemo- and/or radiotherapy.

A prospective, observational study to determine the value of circulating tumor DNA (ctDNA) for predicting the therapeutic effects of the combined modality treatment for colorectal cancer and the patients' long-term prognosis.

Research objects: patients with surgically resectable colorectal cancer. After giving fully informed consent, the prospective participants will undergo the classical combined modality treatment according to NCCN guidelines. Serial analysis of ctDNA will be performed at specific time points including pre-treatment, (post-NCRT for NCRT patients), postoperative week 1, post-ACT, postoperative year 1, 2, and 3. The next-generation sequencing of surgical specimens will be performed as well. Participants will be observed and examined during the entire course of treatment and the follow-up period. The 3 year disease free survival (3y-DFS) will be the primary end-point.

Inclusion Criteria:

1. Patients aged 18 to 75 years old.
2. Patients with surgically resectable colorectal cancer, while without distal metastasis of the disease.
3. Patients with ASA physical status scroe of I to III.
4. Patients who can fully understand the content of the informed consent form and sign it upon their own opinions.
5. Patients who can coordinate with the researchers to undergo the long-term post-treatment rechecks and follow-ups.

Exclusion Criteria:

1. Patient has any underlying or current medical condition, which, in the opinion of the Investigator, would interfere with the evaluation of the patient (e.g., end-stage liver disease, pulmonary hypertension, systemic lupus erythematosis etc.).
2. Patient is pregnant or lactating.
3. Patient has a history of malignancy within 5 years except curatively treated basal cell carcinoma, squamous cell carcinoma in a non-mucosal, ultraviolet exposed area, or cervical carcinoma.
4. Patient is participating in any other clinical trials within 30 days prior to screening.
5. Patient has severe mental illness.
6. Patient has any other conditions, which, in the opinion of the Investigator, would interfere with the evaluation of the subject.