A Study of Cetuximab Plus Raltitrexed for Maintenance Treatment in Advanced Colorectal Cancer

Inclusion Criteria: * 18-75 years old, no gender restriction; * RAS wild-type * Unresectable metastatic colorectal cancer confirmed by histopathology and / or cytology; * Disease stable or improved while on first-line use of FOLFOX/FOLFIRI with cetuximab for 4-6 months; * At least one measurable objective tumor lesion by spiral CT scan，the longest diameter measured ≧ 10 mm，or by conventional CT scan，the diameter measured ≧ 20 mm. * Eastern Cooperative Oncology Group (ECOG) general status score is 0-2; * Life expectancy of at least 3 months; * Blood routine, liver and kidney function within the 7 days before screening meet the following criteria: Absolute neutrophil count ≥ 1.5x10\^9 / L; hemoglobin ≥ 9.0 g / dl; platelet count ≥ 80 x10\^9 / L; total bilirubin ≤ 1.5 times the upper limit of normal (ULN); alanine aminotransferase and aspartate aminotransferase ≤ 2.5 x ULN (≤5 x ULN in patients with liver metastases); ≤3 x ULN in patients with liver metastases (≤5 x ULN in patients with liver metastases); serum creatinine ≤1.5 x ULN; * Agree to sign informed consent. Exclusion Criteria: * BRAF mutant * Symptomatic brain or meningeal metastases (unless patients receive treatment\> 6 months, imaging results are negative within 4 weeks before joining the study, and tumor-related clinical symptoms are stable before joining the study); * Previous malignant disease within five years, with the exception of the cured primary cervical cancer or basal cell carcinoma of the skin; * Chronic intestinal disease, infectious intestinal disease, intestinal obstruction, active clinical severe infection and other diseases; * With ascites * Substance abuse and medical, psychological or social conditions that may interfere with the participation of patients in the study or influence the evaluation of the results of the study; * Unsuitable for the study or other chemotherapy determined by investigator.