Consolidation Chemotherapy for Locally Advanced Mid or Low Rectal Cancer After Neoadjuvant Concurrent Chemoradiotherapy

Inclusion Criteria: 1. Histologically confirmed adenocarcinoma of mid or low rectum 2. Locally advanced rectal cancer confirmed by image (i.e. Magnetic resonance image) * Clinical stage T1-3N1or2 on MRI * Clinical stage cT3N0 (or depth of perirectal invasion by tumor \>5mm on MRI) * Suspicious of circumferential invasion on MRI (or circumferential margin \<1mm) 3. ECOG performance status of 0-2 4. ASA grade ≤ 3 5. An informed consent has been signed by the patient Exclusion Criteria: 1. Upper rectal cancer 2. Clinical stage T1or2N0 on MRI 3. Clinical stage T4Nany on MRI 4. Clinical stage TanyNanyM1 by image or histology 5. The patient received chemotherapy or radiotherapy during the past 6 months 6. The patient received any therapy for colorectal cancer or another malignancy during the past 5 years 7. The patient has severe underlying diseases or poor condition to receive chemotherapy or radiotherapy 8. Pregnant of breastfeeding women 9. The patient who participate in another clinical trial, or receives any drug for the trial 10. Uncontrolled peripheral neuropathy (more than grade 2) 11. Any unhealed wound, fracture, peptic ulcer, or intraabdominal abscess 12. Active gastrointestinal bleeding 13. Patients with an active infection, which needs antibiotic therapy, during the randomization period