Patient：Description of disease (onset time, main symptoms, hospitalization, etc.): As the question, how long can we do PET-CT after chemotherapy? Hospital oncology expert: After chemotherapy for rectal cancer, the regular review is every three months in the first year for chest, abdominal and pelvic CT and CEA, and six months in the second year for chest, abdominal and pelvic CT and CEA, and annually from the third to the fifth year for chest, abdominal and pelvic CT and CEA, and every two years after five years, there is no requirement for PET-CT, but patients with good conditions can have PET-CT every year. There is no requirement for PET-CT, but patients with good conditions can have PET-CT every year, and of course, they can replace all the CT examinations with PET-CT.