Organ Preservation First Strategy and Intentional Watch and Wait for MRI Defined Low-risk Rectal Cancer

Inclusion criteria

• Age ≥ 18 years and ≤85 years
• ECOG Performance status 0-1
• Histologically confirmed diagnosis of adenocarcinoma of the rectum, with tumor differentiation Grade 1-3
• The distance from down verge of tumor to anal-rectal junction (ARJ) ≤4cm based on MRI, or ≤8 cm based on sigmoidoscopy
• Clinical Stage T2 or T3a or T3b and EMVI (-) and MRF (-) and extra-mesorectal metastatic lymph node (-) based on MRI
• The maximum diameter of the tumor is ≤4cm or the circumferential invasion range is less than 1/3 of the intestinal circumference
• No evidence of distant metastases
• No prior pelvic radiation therapy
• No prior chemotherapy or surgery for rectal cancer
• No active infections requiring systemic antibiotic treatment
• ANC > 1.5 cells/mm3, HGB > 10.0 g/dL, PLT > 100,000/mm3, total bilirubin ≤ 1.5 x ULN, AST≤ 3 x ULN, ALT ≤ 4 x ULN
• Patients must read, agree to, and sign a statement of Informed Consent prior to participation in this study.

Exclusion criteria

• Recurrent rectal cancer
• Primary unresectable rectal cancer. A tumor is considered unresectable when invading adjacent organs and an en-bloc resection will not achieve negative margins
• Creatinine level greater than 1.5 times the upper limit of normal
• Patients who have received prior pelvic radiotherapy
• Patients who are unable to undergo an MRI
• Patients with a history of a prior malignancy within the past 5 years, except for well treated basal cell cancer, squamous cell skin cancer, breast cancer, thyroid cancer or small renal cancer, and with DFS >5 years
• Patients with a history of any arterial thrombotic event within the past 6 months. This includes angina (stable or unstable), MI, TIA, or CVA
• Other anticancer or experimental therapy
• Women who are pregnant or breast-feeding
• Patients with any other concurrent medical or psychiatric condition or disease which would make them inappropriate candidates for entry into this study.