Inclusion Criteria:  Histologically confirmed diagnosis of adenocarcinoma of the rectum (AV≤5cm) Clinical ycT2-3N0 based on MRI after neoadjuvant chemoradiotherapy (including long/short-course chemoradiotherapy, total neoadjuvant therapy etc…) No evidence of distant metastases No prior pelvic radiation therapy No prior chemotherapy or surgery for rectal cancer Age 18 to 80 years No active infections requiring systemic antibiotic treatment (oral antibiotics are acceptable at the discretion of the treating physician) Women with childbearing potential who are negative for pregnancy test (urine or blood) and who agree to use effective contraceptive method. A woman of childbearing potential is defined of one who is biologically capable of becoming pregnant. Reliable contraception should be used from trial screening and must be continued throughout the study. Patients must read, agree to, and sign a statement of Informed Consent prior to participation in this study. Patients who do not read or understand Korean are eligible and may be consented according to institutional and federal regulations. Hemoglobin ≥ 10 g/dl (after correction for simple iron deficiency anemia), White blood cells ≥ 4,000/mm3, Platelets ≥ 100,000/mm3, Creatinine ≤ 1.5 mg/dl No significant dysfunction in the heart or lungs: When it is judged that the risk related to surgery due to functional impairment is not high during consultation treatment  Exclusion Criteria:  Metastasis to the liver, lung, brain, bone, abdominal aortic lymph node, subclavian lymph node, inguinal lymph node, etc. at the time of evaluation before treatment Patients with a history of a prior malignancy Patients with serious heart disease and heart failure, severe lung disease or pulmonary insufficiency, active bacterial infection requiring parenteral antibiotic administration and/or other serious medical conditions Patients with any other concurrent medical or psychiatric condition or disease which, in the investigator's judgment, would make them inappropriate candidates for entry into this study. When it is legally impossible to participate in a clinical trial Patients who are pregnant or lactating When existing diseases and disorders are expected to affect the quality of life evaluation after surgery