Non Inferiority Study of Preoperative Chemotherapy Without Pelvic Irradiation for Rectal Cancer

Inclusion Criteria: * Histologically proven middle or low rectal carcinoma, ≤ 10 cm from the anal verge on MRI (sagittal slide) * cT3N0 and/or cT1-T3N+ on pretreatment imaging work up (pelvic contrast enhanced MRI and/or endorectal ultrasound), * Pretreatment predictive circumferential margin \> 2mm on pretreatment imaging work up (pelvic contrast enhanced MRI) * Patients must be 18 years old or older * A World Health Organization (WHO/ECOG) performance status of 0 or 1 * Informed consent signed * Patients of childbearing / reproductive potential should use adequate birth control measures during the study treatment period and for at least 6 months after the last study treatment. A highly effective method of birth control is defined as those which result in low failure rate (i.e. less than 1% per year) when used consistently and correctly. Exclusion Criteria: * Rectal tumor \> 10 cm from the anal verge on MRI (sagittal slide) * cT4 tumor on pretreatment imaging work up (pelvic contrast enhanced MRI and/or endorectal ultrasound) or involvement of external sphincter * Circumferential margin ≤ 2 mm on pretreatment imaging work up (pelvic contrast enhanced MRI) * Metastatic disease * Prior pelvic irradiation or any contraindication to pelvic irradiation * Contraindication to oxaliplatin or irinotecan or 5FU based chemotherapy * Concomitant treatment with warfarin is contraindicated and warafarin must be replaced whenever possible to allow for inclusion. * Recent or concomitant …