Pyridoxine in Preventing Hand-Foot Syndrome in Patients Who Are Receiving Capecitabine for Advanced Colorectal Cancer or Breast Cancer

DISEASE CHARACTERISTICS: * Diagnosis of advanced colorectal or breast carcinoma * Hormone receptor status not specified * Receiving single-agent capecitabine chemotherapy * Measurable disease for response assessment, determined on an individual patient basis, using conventional clinical and/or radiological methods PATIENT CHARACTERISTICS: * ECOG performance status 0-2 * Menopausal status not specified * Life expectancy ≥ 12 weeks * Hemoglobin ≥ 10 g/dL * Platelet count ≥ 100,000 mm\^3 * WBC ≥ 3,000/mm\^3 * ANC ≥ 1,500/mm\^3 * Bilirubin ≤ 1.3 x upper limit of normal (ULN) * Alkaline phosphatase ≤ 5 x ULN * AST and ALT ≤ 5 x ULN * Creatinine ≤ 1.5 x ULN * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception during and for 3 months after completion of study treatment * No other serious or uncontrolled illness which, in the opinion of the investigator, makes it undesirable for the patient to enter the trial * No medical or psychiatric condition which would influence the ability to provide informed consent PRIOR CONCURRENT THERAPY: * See Disease Characteristics * At least 6 weeks since prior investigational agents * Concurrent radiotherapy allowed * No other concurrent chemotherapy or immunotherapy * No concurrent nonsteroidal anti-inflammatory drugs NSAIDs) for the primary purpose of treating hand-foot syndrome (HFS) or cancer * NSAIDs for conditions other than HFS or cancer allowed