Statement: participants of the primary clinical trial may have started flucytosine treatments less than 6 months before study entry
Primary_evidence: Inclusion Criteria:   Biopsy-diagnosed breast cancer with metastasis in multiple organs   Performance Status (World Health Organization :WHO) 0-2   Functions below are maintained in major organs:   Leukocyte count: 4,000/mm3 to 12,000/mm3   Neutrophil count: >2,000/mm3 or more   Platelet count: <100,000/mm3 or more   Hemoglobin: >9.5 g/dL   Total bilirubin: >1.5 mg/dL   AST(GOT): within twice a normal upper value in an institution   AST(GPT): within twice a normal upper value in an institution   BUN: < 25 mg/dL   Creatinine: within a normal upper value in the institution   24 hours creatinine clearance: >50 mL/min (using the Cockcroft-Gault formula)   Women's Ccr = Body weight x (140-Age)/(72 x Serum creatinine) x 0.85   Written informed consent will be obtained for patients for entering this study Exclusion Criteria:   Patients with synchronous multiple cancers   Complicated with infection   Fever from suspected infection   Metastasis to the central nerve system   A history of ischemic cardiac diseases   Active gastrointestinal ulcer   Severe nerve disorder   Women who are potentially pregnant, pregnant, or breast-feeding   Severe drug allergy   Severe suppression of the bone marrow   Severe renal disorder   Being treated with other pyrimidine fluoride antineoplastic agents (including any combination therapy)   Being treated with flucytosine   Complicated with the infection onset which a study doctor assesses to be inappropriate for this study