Metformin for the Treatment of mCRC Patients Undergoing FOLFIRI Plus Target Therapy

Inclusion Criteria: 1. Aged between 20 and 90 years old 2. Patients diagnosed with metastatic colorectal cancer who is going to receive FOLFIRI chemotherapy 3. Female must not be planning to become pregnant or breastfeeding, and not pregnant at any point during treatment. (Contraception is required to participate in this trial) 4. Those without major physiological diseases (example of major cardiovascular disease is acute myocardial infarction; example of major cerebrovascular disease is acute stroke, malignant hypertension, acute kidney failure, acute liver failure) 5. Those who are not allergic to the relevant drugs required for the test 6. Those who can follow the doctor's order to take the medicine 7. Subjects must be willing to sign the consent form 8. Blood sugar level above 80 mg/dL Exclusion Criteria: Subjects who meet any of the following exclusion conditions are not allowed to join the trial 1. Patients other than the above-mentioned main inclusion criteria. 2. Non-native speakers 3. Known allergy to metformin or any of its components. 4. Severe instability in diabetes (ketoacidosis). 5. Blood sugar level lower than 80 mg/dL 6. Heart failure, respiratory insufficiency. 7. inadequate hematopoietic function defined as below: * hemoglobin \< 9 g/dL; * absolute neutrophil count (ANC) \< 1,500/mm3; * platelet count \< 100,000/mm3; 8. inadequate organ functions defined as below: * total bilirubin \> 2 times upper limit of normal (ULN); * hepatic transaminases (ALT and AST) \> 2.5 x ULN; * creatinine \> 1.5 x ULN;