Pemetrexed Alone as Salvage Treatment in Metastatic Colorectal Cancer Patients Who Were Failed After Standard Chemotherapy: A Phase II Single Arm Prospective Study

Inclusion Criteria: 1. Subject is at least 20 years of age. 2. Written and voluntary informed consent understood, signed and dated. 3. They must have refractory or progressive colorectal cancer for which there is no further curative therapy available. 4. Subject able to adhere to the study visit schedule and other protocol requirements. 5. ECOG 0-2 6. At least one measurable lesion that can be accurately assessed by imaging or physical examination at baseline and following up visits. 7. Must have a life expectancy of 3 months or more 8. Demonstrate adequate organ function 9. Negative urine or serum pregnancy test within 28 days of study treatment 10. Be willing to provide fresh tissue for biomarker analysis, and, based on the adequacy of the tissue sample quality for assessment of biomarker status. Exclusion Criteria: 1. ECOG ≥ 3 2. History of malignancy in the last 5 years. 3. Subject has known historical or active infection with HIV, hepatitis B, or hepatitis C. 4. Breast-feeding or pregnant female 5. Patients can not the administration of Folic acid or Vitamin B12. 6. Before treatment with Pemetrexed. 7. Patients who can not swallow oral medication. 8. The most recent treatment with the clinical trial for the drug for 14 days prior to enrollment. 9. Systemic chemotherapy within three weeks after the administration of the last before the test treatment, radiation therapy patients who had been administered. 10. Except for the hair loss, it is induced before cancer treatment, all of toxicity in progress (\> CTCAE1 grade). 11. Upper GI bleeding within registration before 4 weeks of Bowel obstruction or CTCAE3 or 4 grade. 12. Subject who experienced a recent myocardial infarction, including severe/unstable angina pectoris, coronary/peripheral artery bypass graft, uncontrolled hypertension, clinically significant cardiac dysrhythmia or clinically significant electrocardiogram (ECG) abnormality, significant or uncontrolled cardiovascular disease CHF, and cerebrovascular accident or transient ischemic attack, or seizure disorder in the past year.