Phase I study of a novel capecitabine schedule based on the Norton-Simon mathematical model in patients with metastatic breast cancer.

PURPOSE This study was conducted to determine, in patients with advanced-stage breast cancer, the maximum tolerated dose (MTD) of capecitabine administered orally for 7 days followed by a 7-day rest (7/7), a schedule based on a mathematical method for the optimization of anticancer drug scheduling. PATIENTS AND METHODS Eligible patients had measurable, metastatic breast cancer. There was no limit to number of prior treatments. A standard, three-patients-per-cohort dose-escalation scheme used flat-dose capecitabine beginning at 1,500 mg orally twice daily (bid) on a 7/7 schedule. Each cohort was monitored for 28 days before escalation to the next cohort to assess for delayed toxicity. Response was evaluated radiographically every 12 weeks; toxicity was assessed every 2 weeks. RESULTS Twenty-one patients were treated on study. The most frequently reported treatment-related grade 2/3 adverse events were hand-foot syndrome (29%), leukopenia/neutropenia (24%), and fatigue (19%). Grade 3 toxicity was transient and easily managed. Three patients experienced grade 3 hand-foot syndrome; one of these patients had grade 3 diarrhea. There were no grade 4 events. The MTD of capecitabine 7/7 is 2,000 mg twice daily. CONCLUSION As predicted by mathematical modeling, capecitabine dosing for 7 days followed by a 7-day rest is well tolerated. Efficacy of this schedule is being determined in a phase II clinical trial in patients with advanced breast cancer.