The purpose of this study is to compare the efficacy of a novel schedule of an oral anticancer drug, capecitabine, in patients with metastatic breast cancer.

Mathematical models have predicted that 7 days of capecitabine followed by 7 days of rest is an optimal dosing schedule for this drug and previous studies done al Memorial Sloan Kettering Cancer Center support the tolerability of this scheme.

This definitive, randomized trial comparing the efficacy of the new dosage with the conventional dosing schedule in patients with metastatic breast cancer is necessary and we hypothesize it will be superior in terms of efficacy.

Dosing schedules based on mathematical predictions for optimal drug delivery based on efficacy rather than toxicity could facilitate more rapid and economical drug development. This trial is a proof of principle trial of the highest priority.

Inclusion Criteria:

• 1 Subject Inclusion Criteria

  • Informed consent has been obtained.

  • Metastatic breast cancer.

  • Measurable or non-measurable disease per RECIST criteria.

  • Pathologic confirmation of breast cancer.

  • No limit to the number of prior chemotherapy regimens permitted for metastatic disease.

  • At least 3 weeks since prior chemotherapy. Patients should have recovered from all acute toxicity from such therapy (excluding alopecia).

  • Age ≥18.

  • ECOG 0-2

  • Absolute Neutrophil Count (ANC )≥1.0; hemoglobin ≥9, platelets

    ≥75.000

  • AST, ALT and Alkaline phosphatase <2.5x upper limit of normal (or <5x upper limit of normal in the case of liver metastases). Total bilirubin <1.5x upper limit of normal.

  • Estimated creatinine clearance >50ml/min.

  • If female of childbearing potential, pregnancy test is negative and the patient agrees to use an effective method to avoid pregnancy during the study.

Exclusion Criteria:

• HER2 over-expression and/or amplification as determined by immunohistochemistry (3+) or FISH (>2.0).

  • No prior fluoropyrimidine in the metastatic setting. Adjuvant fluoropyrimidine is permitted if >12 months have elapsed since treatment.
  • No restriction for prior hormonal therapy.
  • GI malabsorption syndrome which could impair oral drug absorption.
  • Concurrent use of warfarin is discouraged as drug interactions may make management of INR more difficult.
  • Central nervous system metastases are permitted if previously treated or clinically stable for at least 3 months.
  • Pregnant or nursing patients.
  • Life expectancy <3 months.