Continuous or Intermittent Cetuximab Plus FOLFIRI as First-line Treatment in RAS/BRAF Wild-type mCRC Patients

The goal of this clinical trial is to learn if the application of the chemotherapy FOLFIRI and cetuximab works better when given with scheduled breaks or continuously in adults with metastatic colorectal cancer. The main question it aims to answer is, whether worsening of disease after 12 months of treatment is lower when the treatment is given with breaks or given continuously. It will also answer the question whether the quality of life is better and side effects are less if chemotherapy is given with breaks. Additionally, the treatment breaks will be controlled by blood tests and imaging examinations. A novel blood test will be introduced to investigate, whether worsening of the disease might be detected before the imaging, and whether a quicker reaction by re-starting the therapy would help the patients. Participants will: * receive an established chemotherapy mit FOLFIRI and cetuximab * Receive blood tests every 4 weeks and imaging investigations every 12 weeks * fill out questionnaires to report their quality of life