Inclusion Criteria:

        1.1 Inclusion criteria for pre-screening phase:

          -  Untreated advanced metastatic colorectal cancer patients

          -  Adequate tissue to evaluate for genotyping (10 x 10µm thick formalin fixed paraffin
             embedded tissue sections and one corresponding HE stained slide or a FFPE tumor block)

        1.2 Inclusion criteria for treatment phase:

        Patients must fulfill all criteria listed below prior to enrolment in the study:

          -  Untreated wild-type KRAS metastatic colorectal cancer

          -  Previous adjuvant therapy must have been completed > 6 months before therapy
             initiation on this study

          -  Age >18 years

          -  Measureable disease with CT or MRI

          -  ECOG performance status of 0-2

          -  Adequate organ function

               -  Hematologic:

                    -  Absolute neutrophil count > 1,500/µL

                    -  Hemoglobin >9 mg/dl

                    -  Platelet count >100,000 /µl

               -  Renal:

                    -  Serum creatinine <1.5 x Upper limit of normal (UPN) or estimated clearance >
                       30 ml/min

               -  Hepatic:

                    -  Serum bilirubin < 1.5 mg/dl

        Exclusion Criteria:

          -  Creatinine clearance below 30 ml/min

          -  Patients with a history of other malignancies within 2 years prior to study entry,
             except for adequately treated carcinoma in situ of the cervix; basal or squamous cell
             skin cancer; low grade, early stage localized prostate cancer treated surgically with
             curative intent; good prognosis DCIS of the breast treated with lumpectomy alone with
             curative intent.

          -  Patients with a history of severe cardiac disease; e.g. NYHA Functional Class III or
             IV heart failure, myocardial infarction within 6 months, ventricular tachyarrhythmias
             requiring ongoing treatment, or unstable angina.

          -  Other known co-morbidity with the potential to dominate survival

          -  Hypersensitivity with anaphylactic reaction to humanized monoclonal antibodies or any
             of the applied drugs

          -  Pregnant or breast feeding women

          -  Any co-existing medical or psychological condition that would preclude participation
             in the study or compromise ability to give informed consent.