Inclusion Criteria:

          -  Histologically confirmed, UICC stage IV metastatic adenocarcinoma of the colon or
             rectum

          -  Primarily non-resectable metastases or surgical resection refused by the patient

          -  RAS mutation determined by the local pathology

          -  Age ≥18

          -  ECOG performance status 0-2

          -  Patients suitable for chemotherapy administration

          -  Patient's written declaration of consent obtained

          -  Estimated life expectancy > 3 months

          -  Presence of at least one measurable reference lesion according to the RECIST 1.1
             criteria

          -  Primary tumor tissue available and patient consents to storage and molecular and
             genetic profiling of tumor material. Molecular profiling of blood samples is
             optionally performed.

          -  Adequate bone marrow function:

               -  Leukocytes ≥ 3.0 x 109/L with neutrophils ≥ 1.5 x 109/L

               -  Thrombocytes ≥ 100 x 109/L

               -  Haemoglobin ≥ 5.6 mmol/L (equivalent to 9 g/dL)

          -  Adequate hepatic function:

               -  Serum bilirubin ≤ 1.5 x upper limit of normal (ULN)

               -  ALAT and ASAT ≤ 2.5 x ULN (in the presence of hepatic metastases, ALAT and ASAT ≤
                  5 x ULN)

          -  Adequate renal function:

             ▫ Creatinine clearance (calculated according to Cockcroft and Gault) ≥ 50 mL/min

          -  No previous chemotherapy for metastatic disease. Patient with need of immediate
             treatment (high tumor load, symptoms) may have received one application of FOLFIRI
             prior to study treatment.

        Exclusion Criteria:

          -  Previous chemotherapy for metastatic disease with the exception of one cycle of
             FOLFIRI (e.g. while waiting for the result of RAS mutation frequency).

          -  Patients planned to be treated with FOLFOX or another oxaliplatin-based regimen as
             first-line treatment

          -  Primarily resectable metastases and the patient agrees to resection

          -  Grade III or IV heart failure (NYHA classification)

          -  Medical or psychological impairments associated with restricted ability to give
             consent or not allowing conduct of the study

          -  Previous chemotherapy for the colorectal cancer with the exception of adjuvant
             treatment, completed at least 6 months before entering the study

          -  Participation in an investigational clinical study or experimental drug treatment
             within 30 days prior to study inclusion or within a period of 5 half-lives of the
             substances administered in the investigational clinical study or during an
             experimental drug treatment prior to inclusion in the study, depending on which period
             is longest

          -  Known hypersensitivity or allergic reaction to any of the following substances:
             5-fluorouracil, folinic acid, panitumumab, irinotecan, and chemically related
             substances and/or hypersensitivity to any of the excipients of any of the
             aforementioned substances including known hypersensitivity reactions to monoclonal
             antibodies NCI CTCAE Grade ≥ 3.

          -  Known hypersensitivity to Chinese hamster ovary cell (CHO) - cellular products or
             other recombinant human or humanised monoclonal antibodies

          -  History of uncontrolled bronchial asthma

          -  Patients with interstitial pneumonitis or pulmonary fibrosis

          -  Patients with known brain metastasis

          -  History of acute or subacute intestinal occlusion or chronic inflammatory bowel
             disease or chronic diarrhoea

          -  Symptomatic peritoneal carcinomatosis

          -  Severe, non-healing wounds, ulcers or bone fractures

          -  Patients with acute or chronic infection requiring systemic therapy

          -  Known history of positive testing for human immunodeficiency virus (HIV) or known
             acquired immunodeficiency syndrome (AIDS)

          -  Active or chronic Hepatitis B virus (HBV) or hepatitis C virus (HCV) infection
             (positive HBV surface antigen or HCV RNA if anti-HCV antibody screening test positive;
             serologic tests required in patients who receive study treatment).

          -  Known DPD deficiency (specific screening not required)

          -  Known glucuronidation deficiency (Gilbert's syndrome);(specific screening not required

          -  Treatment with sorivudine or brivudine within 28 days before study enrollment or
             requirement for concomitant antiviral treatment with sorivudine or brivudine

          -  History of a second primary malignancy during the past 5 years before inclusion in the
             study or during participation in the study, with the exception of a basal cell or
             squamous cell carcinoma of the skin or cervical carcinoma in situ, if these were
             treated curatively.

          -  Known previous or ongoing alcohol or drug abuse

          -  Pregnant or breast-feeding patients

          -  Any other severe concomitant disease or disorder which, in the investigator's opinion,
             could influence the patient's ability to participate in the study or influence his/her
             safety during the study or interfere with interpretation of study results

          -  Both, absent and restricted legal capacity