MoLiMoR - A Study With FOLFIRI-based First-line Therapy With or Without Intermittent Cetuximab

Inclusion Criteria: * Histologically confirmed, UICC stage IV adenocarcinoma of the left-sided colon or rectum with metastases (metastatic colorectal cancer), primarily non-resectable, confirmed RAS mutations proven in the primary tumor or metastasis (KRAS ans NRAS exon 2, 3, 4) * Age ≥ 18 years on day of signing informed consent * No previous chemotherapy for metastatic disease (1- 2 cycles FOLFIRI or mFOLFIRI are permitted before enrolment until RAS status is determined) * Patients suitable for chemotherapy administration * ECOG (Eastern Cooperative Oncology Group) status 0-1 * Consent to liquid biopsy and mutation analysis * Estimated life expectancy \> 3 months * Presence of at least one measurable reference lesion according to the RECIST 1.1 criteria (chest CT and abdominal CT 4 weeks or less before enrollment) * Adequate bone marrow function defined as: Leukocytes 3.0 x 10 9/L with neutrophils 1.5 x 10 9/L, Thrombocytes 100 x 10 9/L, Hemoglobin 9 g/dL * Adequate hepatic function defined as: Serum bilirubin 1.5 x ULN (Upper limit of normal), ALAT (Alanine-aminotransferase (= SGPT = serum glutamate pyruvate transaminase) and ASAT (aspartate-aminotransferase (= SGOT = serum glutamate oxalacetate transaminase) 2.5 x ULN (Upper limit of normal) (in the presence of hepatic metastases, ALAT and ASAT 5 x ULN) * Adequate renal function: Creatinine clearance ≥ 50 mL/min * Adequate cardiac function defined as Normal ECG and echocardiogram with a left ventricular ejection fraction…