Dosage of Capecitabine and Cyclophosphamide Combination Therapy in Patients with Metastatic Breast Cancer

Background: Capecitabine is a highly effective and well-tolerated treatment for metastatic breast cancer (MBC) and extends survival when combined with docetaxel. Capecitabine and cyclophosphamide are orally administered and have preclinical synergy and non-overlapping toxicities. Patients and Methods: Sixteen pretreated MBC patients received escalating doses of oral capecitabine 628 to 829 mg/m 2 twice daily (bid) plus oral cyclophosphamide 33 to 50 mg/m 2 bid, on days 1 to 14 every 21 days. Results: Among the ten patients receiving capecitabine/cyclophosphamide 829/33 mg/m 2 bid on days 1 to 14, two experienced dose-limiting toxicities (DLT, treatment delay >1 week due to grade 2 leukopenia). Because neither patient developed further grade >1 toxicity and none of the patients experienced grade 3/4 toxicities or further DLTs, this dose level is the recommended regimen, producing partial responses in two of five evaluable patients. Conclusion: The recommended all oral capecitabine/cyclophosphamide combination regimen is well tolerated and active in MBC, and is being evaluated in a phase II study in anthracycline-pretreated MBC.