Phase II Trial of Combination Therapy With Bevacizumab and S-1 in Elderly Patients With Unresectable or Recurrent Colorectal Cancer (BASIC)

Inclusion Criteria: 1. Histologically confirmed colorectal carcinoma with inoperable, locally advanced, or metastatic disease, not amenable to curative therapy 2. Measurable disease or non-measurable but assessable disease according to the Response Evaluation Criteria in Solid Tumors (RECIST) 3. Patients with no previous treatment (radiotherapy or chemotherapy). Patients who have received postoperative adjuvant chemotherapy are eligible if relapse is diagnosed more than 180 days after the end of such treatment. 4. Treatment with FOLFIRI and FOLFOX is not indicated. 5. Age \>65 years 6. Life expectancy of at least 3 months 7. ECOG PS of 0, 1, or 2 8. Adequate function of major organs as defined below: 1. Hemoglobin \>9.0 g/dL 2. White blood cell count \>3,500/mm3, \<12,000/mm3 3. Neutrophil count \>1,500/mm3 4. Platelet count \>100,000/mm3 5. Total bilirubin \<1.5 mg/dL 6. AST and ALT \<100 U/L (\<200 U/L in patients with liver metastasis) 7. Serum creatinine \<1.2 mg/dL 8. Creatinine clearance estimate by the Cockcroft-Gault method \>50 mL/min 9. Able to take capsules orally. 10. No electrocardiographic abnormalities within 28 days before enrollment that would clinically preclude the execution of the study, as judged by the investigator. 11. Voluntary written informed consent. Exclusion Criteria: 1. Serious drug hypersensitivity or a history of drug allergy 2. Active double cancer 3. Active infections (e.g., patients with pyrexia of 38℃ or higher) 4. Uncontrolled hypertension 5. Serious complications (e.g., pulmonary fibrosis, interstitial pneumonitis, heart failure, renal failure, hepatic failure, or poorly controlled diabetes) 6. Moderate or severe ascites or pleural effusion requiring treatment 7. Watery diarrhea 8. Treatment with flucytosine 9. Metastasis to the CNS 10. Pregnant women, possibly pregnant women, women wishing to become pregnant, and nursing mothers. Men who are currently attempting to conceive children. 11. Severe mental disorder 12. Continuous treatment with steroids 13. Urine dipstick for proteinuria should be \<2+ 14. Thrombosis, cerebral infarction, myocardial infarction, or pulmonary embolism 15. Major surgical procedure, open biopsy, or clinically significant traumatic injury within 4 weeks 16. Long-term daily treatment with aspirin (\>325 mg/day) 17. History or evidence of inherited bleeding diathesis or coagulopathy with the risk of bleeding 18. Judged ineligible for participation in the study by the investigator for safety reasons.