GRECCAR 8: Primary Tumor Resection in Rectal Cancer With Unresectable Metastasis

Inclusion Criteria: * Non-complicated primary tumor (i.e. tumor without obstruction, bleeding, abscess or perforation requiring emergency surgery and/or contra-indicating first-line chemotherapy) * Unresectable synchronous metastases * ECOG performance status 0-1 * Rectal adenocarcinoma (\<15 cm from the anal verge) with few or no symptoms and unresectable metastasis (assessed by the investigator) unsuitable for curative treatment * No known unresectable primary tumor (with clear margin \>1mm) on CT-scan and MRI * No disease progression under chemotherapy (for at least 4 cycles); * Assessment of KRAS status before randomization (wild type or mutated); * Life expectancy without cancer \>2 years * White blood cell count ≥ 3 x 109/L, with neutrophils ≥ 1,5 x 109/L, platelet count ≥ 100 x 109/L, hemoglobin°≥ 9 g/dL (5,6 mmol/l) * Total bilirubin ≤ 1.5 x ULN (upper limit of normal), ASAT and ALAT ≤ 2.5 x ULN, alkaline phosphatase°≤°1.5°x ULN, serum creatinine ≤ 1.5 x ULN; * Age ≥ 18 years ≤ 75 years * Patients with childbearing potential should use effective contraception during the study and up 6 months after the end of chemotherapy * Covered by a Health System where applicable, and/or in compliance with the recommendations of the national laws in force relating to biomedical research; * Signed written informed consent obtained prior to any study-specific screening procedures Exclusion Criteria: * Rectal tumor operated before inclusion * Symptoms related to the rectal tumor requiring first intention rectal surgery (appreciated by investigator) * Contra-indication for surgery * Resectable metastases * Complicated (obstruction, bleeding, abscess, perforation) primary tumor requiring emergency surgery and/or contra-indicating first line-chemotherapy * Non-resectable primary tumor (with wild margin) * Age \> 75 years \< 18 years * ECOG performance status \> 2 * Under nutrition (albumin \< 30 g/l) * Peritoneal carcinomatosis * Disease progression under chemotherapy (RECIST 1.1 criteria) * Known hypersensitivity reaction or specific contraindications to any of the components of study treatments * Clinically relevant coronary artery disease or history of myocardial infarction in the last 12 months, or high risk of uncontrolled arrhythmia * Pregnancy (absence to be confirmed by ß-hCG test) or breast-feeding; * Previous malignancy in the last 5 years * Medical, geographical, sociological, psychological or legal conditions that would prevent the patient from completing the study or signing the informed consent; in the investigator's opinion * Any significant disease which, in the investigator's opinion, excludes the patient from the study * Under an administrative or legal supervision.