Immunopet Imaging With Zr-89-Cetuximab In Patients With Advanced Colorectal Cancer

11102 Background: Inhibition of epidermal growth factor receptor (EGFR) with cetuximab is part of treatment for patients with wild type (wt) KRAS advanced colorectal cancer (mCRC). Sixty percent of these patients do not benefit from cetuximab treatment. Potential causes include mutations in the EGF signaling cascade or other RAS mutations. Alternatively, pharmacokinetic factors like sequestration of cetuximab in organs with high EGFR expression such as liver could lead to sub-therapeutic intratumoral drug levels. We performed an exploratory study to evaluate biodistribution and tumor uptake using Positron Emission Tomography (PET) with 89Zr labeled cetuximab in patients with wt KRAS mCRC. Methods: Eight patients with wt KRAS mCRC who were candidate for cetuximab monotherapy, received 37 ± 1 MBq 89Zr - cetuximab immediately after the first therapeutic dose of cetuximab. Serial whole body PET was performed from one hour to 10 days post injection (p.i.). Non-hepatic tumor lesions were visually assessed as po...