[Two cases of KRAS wild-type unresectable or recurrent colorectal cancer effectively treated by cetuximab after progression of prior chemotherapy].

Cetuximab, an anti-EGFR human/mouse chimeric antibody, has just been approved in Japan for patients with EGFR positive unresectable or recurrent colorectal cancer, as monotherapy or in combination with irinotecan. We reported two cases of unresectable or recurrent colorectal cancer effectively treated by cetuximab after the progression of the prior chemotherapy. Case 1: A51-year-old male suffered from sigmoid colon cancer with synchronous liver metastases. He received cetuximab plus irinotecan combination therapy in the third-line setting. Amonth after the initiation of the chemotherapy, abdominal CT showed tumor shrinkage of liver metastases. Case 2: A57-year-old female suffered from sigmoid colon cancer with metachronous liver, ovarian metastases, ascites and pleural effusion. Her performance status(PS)according to ECOG performance scale was 1, and she complained of dyspnea on exertion. She received cetuximab monotherapy in the fourth-line setting. Five weeks after initiation of chemotherapy, her chest, abdominal and pelvic CT showed tumor shrinkage of the liver metastases and the reduction of both ascites and pleural effusion, together with resolution of her dyspnea on exertion. Before cetuximab administration, we investigated KRAS status on cancer tissue previously resected in the above 2 cases, which showed KRAS wild-type. Cetuximab could be effective for KRAS wild-type colorectal cancer, as well as the previous reports from Western countries.