A case of heterogeneous sensitivity to panitumumab in cetuximab-refractory colorectal adenocarcinoma metastases

We present the case of a 43-year-old-man with wild-type KRAS and BRAF colorectal adenocarcinoma that was metastatic to the liver and lung. The patient initially received neoadjuvant chemotherapy with FOLFOX and bevacizumab, followed by surgical resection of the primary tumor and hepatic metastases. His disease recurred shortly after surgery and he was treated with FOLFIRI plus the anti-EGFR antibody cetuximab. After this regimen failed to arrest his disease progression, treatment with FOLFIRI in combination with another anti-EGFR antibody, panitumumab was started. While on this therapy, the patient's lung nodules remained largely stable but metastatic lesions within the liver continued to progress. Our case highlights the differences between panitumumab and cetuximab, and contemplates the possible explanations for this patient's apparently heterogeneous disease progression within the liver despite stabilization of multiple pulmonary nodules.