Inclusion Criteria:  Written informed consent to participate in the study Patients ≥ 18 years at the time of signing the informed consent Histologically confirmed (in primary tumour or metastasis) UICC stage IV metastatic adenocarcinoma of the colon or rectum (mCRC) with primarily unresectable metastases RAS mutant CRC (as determined by local pathology in tissue of primary tumour or metastasis) At least one measurable lesion according to RECIST version 1.1 in a CT/MRI scan performed within 28 days prior to start of systemic treatment (first cycle of induction treatment) ECOG performance status 0-1  Patients planned to receive chemotherapy with FOLFOXIRI plus bevacizumab as first-line treatment of metastatic disease. De-escalation of FOLFOXIRI to FOLFIRI or FOLFOX is allowed in case of toxicity.  Patients can also be included if they had already received ≤ 4 cycles of induction/conversion therapy with FOLFOXIRI plus bevacizumab (including those patients in whom FOLFOXIRI has been de-escalated to FOLFIRI or FOLFOX due to toxicity) and the first restaging has not been conducted prior to randomization.  Completion of adjuvant therapy for colorectal cancer > 3 months prior to start of systemic treatment (first cycle of induction treatment). Patient's ability for treatment with FOLFOXIRI and bevacizumab according to participating physician's judgement.  Exclusion Criteria:  Pregnant or breast-feeding women. Females of childbearing potential (FCBPs) who do not practice adequate contraceptive measures as required according to SmPCs of the administered medicinal products. Contraindication to intensive chemotherapy with FOLFOXIRI plus bevacizumab Contraindications to treatment with 5-FU, oxaliplatin, folinic acid, irinotecan (FOLFOXIRI) and/or bevacizumab according to SmPCs of the administered medicinal products. Patients with confirmed cerebral metastasis. In case of clinical suspicion of brain metastasis, a cranial CT or MRI must be performed to rule out brain metastasis before study inclusion. Documentation of > 5 lung metastases (however, no limitation for the number of metastases in the liver) Isolated distant nodal metastasis, isolated peritoneal metastasis or isolated bone metastasis Limited legal capacity