The Role of Surgery of the Primary Tumour in Patients With Synchronous Unresectable Metastases of Colorectal Cancer

Inclusion Criteria: * Histological proof of colorectal cancer * Resectable primary tumour in situ with unresectable distant metastases * No indication for neo-adjuvant (chemo)radiation * No severe signs or symptoms related to the primary tumour (i.e. severe bleeding, obstruction, severe abdominal pain) that require immediate surgery or other symptomatic treatment (e.g. stenting) * No prior systemic treatment for advanced disease * Age ≥ 18 years * WHO performance status 0-2 * Laboratory values obtained ≤ 4 weeks prior to randomization: Adequate bone marrow function (Hb ≥ 6.0 mmol/L, absolute neutrophil count ≥ 1.5 x 109/L, platelets ≥ 100 x 109/L), renal function (serum creatinine ≤ 1.5x ULN and creatinine clearance, Cockroft formula, ≥ 30 ml/min), liver function (serum bilirubin ≤ 2 x ULN, serum transaminases ≤ 3 x ULN without presence of liver metastases or ≤ 5x ULN with presence of liver metastases) * Expected adequacy of follow-up * Written informed consent * CT scan abdomen and CT thorax/X-thorax performed ≤ 4 weeks prior to randomization Exclusion Criteria: * Pregnancy, lactation * Unresectable primary tumour (i.e. neurovascular encasement, substantial ingrowth in pancreatic head), or any condition preventing the safety or feasibility of resection of the primary tumour, i.e. massive ascites or extensive peritoneal disease * Requirement of neoadjuvant (chmo)radiation therapy * Second primary malignancy within the past 5 years with the exception of adequately treated in situ carcinoma of any organ or basal cell carcinoma of the skin * Any medical condition that prevents the safe administration of systemic treatment * Previous intolerance of fluoropyrimidines, known dihydropyrimidine dehydrogenase (DPD) deficiency * Planned radical resection of all metastatic disease * Uncontrolled hypertension, i.e. values consistently \> 150/100 mmHg * Use of ≥ 3 antihypertensive drugs * Significant cardiovascular disease \< 1 yr before randomization (symptomatic congestive heart failure, myocardial infarction, unstable angina pectoris, serious uncontrolled cardiac arrhythmia, cerebro vascular event) * Chronic active infection * Concurrent treatment with any other anti-cancer therapy as described per protocol