Chemoradiation and Consolidation Chemotherapy With or Without Oxaliplatin for Distal Rectal Cancer and Watch and Wait

Inclusion Criteria: 1. Age ≥18 years; 2. ECOG 0-2 or KPS≥70; 3. Primary rectal adenocarcinoma (biopsy confirmed) within the reach of digital rectal examination (at least lower tip/border) by the attending colorectal surgeon; 4. Endoscopic documentation; 5. Abdominal and chest CT scans showing no evidence of metastatic disease; 6. High-resolution magnetic resonance images performed at either 1.5T or 3.0T system using a phased array surface coil with: sagittal T2 images including the anal verge and the sacrum; axial oblique T2 weighted images acquired in a plane perpendicular to the long axis of the rectal wall guided by the sagittal images; coronal images acquired in parallel to the anal canal plane. Small field of view (16-18cm), 3mm section thickness, increased matrix size and increased number of signal averages are required; 7. Radiological defining criteria (centralized): 1. Lower edge of tumor at the level (max. 1cm distance) or below the anorectal ring defined at sagittal or coronal views; 2. mrT2, mrT3 (any subclassification) 3. mrN0-1 (≤3 radiologically positive lymph nodes) 4. mrEMVI: any status 5. mrMRF: any status Exclusion Criteria: 1. Pregnancy 2. ECOG ≥3 or KPS\<70 3. Unwilling to consent 4. Metastatic disease (any kind; internal iliac and obturator nodes are considered local disease and not metastatic disease and therefore will not be considered as exclusion criteria) 5. mrT4 or mrN2 6. Previous pelvic irradiation 7. Baseline neuropathy 8. Receiving treatment of other anti-cancer drug or methods 9. Presence of uncontrolled life threatening diseases