The purpose of this study is to investigate the response rate of cetuximab plus irinotecan every 2 weeks in patients harboring wild-type KRAS with and without detectable EGFR-expressing metastatic CRC after failure to irinotecan in an exploratory manner.

Twenty patients with positive-EGFR results and 20 patients with negative-EGFR results will be accrued in this study. All patients should have wild-type KRAS.

Inclusion Criteria:

• Colorectal adenocarcinoma, Wild KRAS, 18-75 yr
• Estimated life expectancy of more than 3 months
• ECOG performance status of 0 to 1 at study entry
• Adequate bone marrow function
• Adequate liver function
• Documented progression during or within 3 months of irinotecan-containing regimens as a first-line chemotherapy
• Immunohistochemical evidence of a presence or absence of EGFR expression by PharmDx Kit
• Informed Consent

Exclusion Criteria:

• Central nervous system (CNS) metastases or prior radiation for CNS metastases.
• Intestinal obstruction or impending intestinal obstruction due to peritoneal carcinomatosis
• Surgery (excluding biopsy for diagnosis) during 4 weeks prior to inclusion in the study.
• Evidence of gastrointestinal bleeding
• Exposure to Cetuximab
• Prior administration of monoclonal antibodies, EGFR signal transduction inhibitors or EGFR-targeted treatment
• KRAS mutant Status
• Patients with serious toxicity to previous irinotecan-based chemotherapy
• Other serious illness or medical conditions