Recently, the American Society of Clinical Oncology reviewed and endorsed the methodological rigour of the Cancer Care Ontario (CCO) guidelines for follow-up, surveillance prognosis and secondary prevention for patients with colorectal cancer. A statement was issued. The main recommendations of the guidelines are: * We should guide clinical surveillance based on the risk of recurrence and the functional status of the patient (the first 2-4 years are very important). ※ History taking, physical examination and carcinoembryonic antigen testing should be performed every 3-6 months and monitored continuously for 5 years. Patients with a high risk of recurrence should be examined more frequently. ※ In most cases, computed tomography (CT of the chest and abdomen) should be reviewed once a year with 3 years of continuous monitoring. ※ Positron emission computed tomography (PET) should not be used for surveillance unless it is for a clinical trial. ※ Colonoscopy should be performed 1 year after the initial procedure and every 5 years thereafter if there are no abnormal findings at the previous examination. If colonoscopy was not performed before definitive diagnosis, then colonoscopy should be performed once after completion of adjuvant therapy (less than 1 year). * Secondary prevention (including maintaining a healthy weight and an active lifestyle) is recommended. * A patient should not be monitored if he or she cannot tolerate surgery or systemic therapy due to a combination of other serious diseases. The treatment plan developed by the specialist should provide direction for follow-up monitoring and treatment by the non-specialist.