Conversion Therapy Using mFOLFOX6 With Panitumumab for Unresectable Liver Metastases From Multiple Colorectal Cancers With Familial Adenomatous Polyposis

A 39-year-old man received a diagnosis of unresectable multiple liver metastases from multiple colorectal cancers with familial adenomatous polyposis. After construction of an ileostomy, modified FOLFOX6 (mFOLFOX6) with panitumumab was administrated because rectal cancer and sigmoid colon cancer are KRAS wild type. The 13 courses of chemotherapy resulted in a marked reduction in the size of liver metastases and sigmoid colon cancer. Consequently, curative resection with total colectomy, ileal pouch anal anastomosis, and liver metastasis resection with radiofrequency ablation was performed. Progression of KRAS wild-type rectal cancer after chemotherapy suggested that each clone from rectal and sigmoid colon cancer might have a different sensitivity to epidermal growth factor receptor antibody. Immunohistochemical analysis revealed loss of PTEN expression in rectal cancer compared with liver metastases from sigmoid colon cancer, showing that the difference of mFOLFOX6 with panitumumab might be related to activation of the PI3K-AKT pathway.