• Histologically or cytologically confirmed adenocarcinoma of the metastatic colorectal cancer;

• Previously treated with fluorouracil-, oxaliplatin-, and irinotecan-based chemotherapy, and anti-vascular endothelial growth factor (anti-VEGF) biological therapy;

• The RAS wild-type patients need to receive anti-EGFR therapy;

• Presence of at least one measurable tumor lesion which is defined as lesion that can be measured in at least one dimension (longest diameter) with a minimum size of : 10mm by CT scan, MRI and PET-CT(no less than double the slice thickness and a minimum of 10mm)(according to RECIST guideline version 1.1);

• Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0, 1 or 2;

• Investigators prescribe Lonsurf® for metastatic colorectal cancer patients who had prior treatment with Anti-VEGF and Anti-EGFR agent on routine basis. Depending on RAS status, patients with RAS mutant receive Lonsurf® as 3rd line treatment, those with RAS wild type receive Lonsurf® as 3rd/4th line treatment;

• Patients received either oxaliplatin or irinotecan.