Disparity Between In Vivo EGFR Expression and 89Zr-Labeled Cetuximab Uptake Assessed

The epidermal growth factor receptor (EGFR) is highly expressed in a significant number of human malignancies, and its ex-pression is associated with tumor aggressiveness and overall treatment resistance. The monoclonal antibody cetuximab is increasingly used in clinical settings as a treatment modality in combination with more conventional therapies, such as ra-dio- and chemotherapy. Currently, little is known about tumor-specific uptake and overall pharmacokinetics. Noninvasive quantification of cetuximab uptake could provide important diag-nostic information for patient selection and therapy evaluation. To this end,wehavedevelopedandvalidatedanovel probeusing cetuximab labeled with the long-lived positron emitter 89Zr for PET imaging. Methods: Tumor cell lines with varying EGFR ex-pression levels were used for in vivo tumor imaging experiments. PET with 89Zr-labeled cetuximab (3.75 6 0.14 MBq) was per