Optimalisatie van de behandeling van uitgezaaide darmkanker met cetuximab middels opname metingen van 89Zr gelabeld cetuximab mbv PET.

Interventions: Patients will be treated with cetuximab. For pharmacodynamic purposes PET-imaging with 89Zr-labelled cetuximab will be performed. In addition, two [18F-]-FDG PET-CT will be performed to explore early response. Patients will undergo blood sampling and two skin biopsies for pharmacodynamic purposes of 89Zr-labelled cetuximab and kinase activity profiles, respectively. Primary outcome(s): To demonstrate uptake of 89Zr-cetuximab in non-hepatic tumor lesions using immuno-PET when administered during the loading dose of cetuximab. Part two - Primary objective: To investigate whether there is an association between uptake of cetuximab in non-hepatic tumor lesions and response according to RECIST 1.1 criteria. Study Design: N/A: single arm study, Open (masking not used), N/A , unknown, Parallel