IMPROVE: Circulating Tumor DNA Analysis to Optimize Treatment for Patients With Colorectal Cancer

Part I: Surgery Inclusion Criteria: * Colon or rectal cancer, clinical tumor stage I-III * Patient able to understand and sign written informed consent * Scheduled for curative intended resectional surgery Exclusion Criteria: * Hereditary colorectal cancer linked to familial colonic polyposis or Lynch syndrome * Inflammatory bowel disease (Crohn's disease or ulcerative colitis) * Verified distant metastases * Malignant colorectal polyps diagnosed after polypectomy * Patients who are unlikely to comply with the protocol (e.g. uncooperative attitude, inability to return for subsequent visits) and/or otherwise considered by the Investigator to be unlikely to complete the study Part II: Surveillance: Inclusion criteria: One of the following: * TNM stage III CRC, * or TNM stage II CRC and risk factors qualifying for adjuvant chemotherapy, * or TNM stage I or stage II CRC without risk factors, but ctDNA positive in the post-operative day14 plasma sample. Inclusion requires that the patient declined participation in the IMPROVE IT trial. Exclusion criteria: * Synchronous colorectal and non-colorectal cancer diagnosed per-operative (except skin cancer other than melanoma) * Other cancers (excluding colorectal cancer or skin cancer other than melanoma) within 3 years from screening