Rechallenge of Prior Regimen in Third or Later-line Chemotherapy in Metastatic Colorectal Cancer

Inclusion Criteria 1. Patients age between 18 and 80 years 2. Histologically confirmed metastatic colorectal cancer (mCRC) 3. An Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 4. Treatment failure to at least two lines of chemotherapy (regimens should include oxaliplatin, fluorouracil and irinotecan); progression free survival (PFS) of prior oxaliplatin or irinotecan-based chemotherapy should be at least four months without any unrecoverable toxicity. Prior target therapy was acceptable 5. For those who received other anti-tumor treatment, the toxicity should have been restored, with the time interval from last dose of cytotoxic drugs, radiation or surgery (the wound should be healed completely) ≥3 weeks 6. Life expectancy≥12 weeks 7. At least one measurable lesion as defined by RECIST 1.1 8. Acceptable hematologic, hepatic, and renal function within 7 days from screening: the blood ANC count≥1.5\*10\^9/L; hemoglobin≥9.0 g/dl, the blood platelet count≥80 x 10\^9/L, total bilirubin\<1.5\*upper limits of normal(ULN), ALT and AST\<2.5\*ULN(\< 5 \*ULN for patients with live metastasis), endogenous creatinine clearance rate\>50ml/min 9. Targeted drugs are currently not suitable or affordable Exclusion Criteria 1. Receiving other systemic anti-cancer treatment within 3 weeks 2. Prior radiation therapy of target measurable lesion 3. Presence of Grade III or IV chemo-related toxicity in previous treatment without recovery to Grade II or less 4. With other malignant tumor in 5 years; except for cured cervical carcinoma in situ or basal cell carcinoma 5. Symptomatic intracranial or meningeal metastasis 6. History of uncontrolled seizures, central nervous system dysfunction or mental disorder 7. Uncontrolled pleural or peritoneal effusion 8. Severe life-threatening concomitant disease that might impair the safety of patients or affect the completion of treatment, according to the researcher's judgment