Inclusion Criteria:

- histologically confirmed metastatic colorectal adenocarcinoma

- KRAS wild-type tumors, EGFR-expressing or EGFR-nonexpressing by immunohistochemistry;

- has measurable lesion, at least 1cm in diametre by CT or MRI, at least 2cm diametre
by physical examination or other iconography

- ECOG performance status 0 to 1

- Failure (disease progression/discontinuation due to toxicity) of fluoropyrimidine and
oxaliplatin treatment,stop at least one month thereafter, irinotecan-naïve

Exclusion Criteria:

- Previous irinotecan or anti-EGFR therapies were excluded

- hematologic function: hemoglobin, less than 90g per liter; neutrophil count, less
than 1500 per cubic millimeter; and platelet count, less than 100,000 per cubic
millimeter

- liver function: bilirubin, more than 1.0 times the upper limit of normal; aspartate
aminotransferase and alanine aminotransferase, more than 5.0 times and 2.5 times the
upper limit of normal with hepatic metastasis or not

- Renal function: serum creatinine, more than 1.5 times the upper limit of normal

- Patients with symptomatic central nervous system metastases were excluded