Phase I Trial of Everolimus and Capecitabine in Metastatic HER2 − Breast Cancer

Background The mammalian target of rapamycin (mTOR) pathway is a driver of breast tumorigenesis. The mTOR inhibitor everolimus reverses antihormonal therapy resistance and is an approved therapy for metastatic breast cancer. A synergistic effect with fluoropyrimidine has been suggested. The present study evaluated the safety and tolerability of an all-oral combination of everolimus and capecitabine for metastatic breast cancer (MBC). Patients and Methods MBC patients naive to capecitabine and mTOR inhibitors who had received ≤ 3 previous chemotherapy regimens in the metastatic setting were eligible for the present study. The patients were scheduled to receive capecitabine 825 mg/m 2 twice daily for 14 days in a 21-day cycle, combined with everolimus in 5 separate dose cohorts: 2.5 mg every other day, 2.5 mg daily, 5 mg daily, 7.5 mg daily, and 10 mg daily. A 3+3 design was used. The maximum tolerated dose was based on the dose-limiting toxicity of everolimus plus capecitabine. Results A total of 18 patients were enrolled in the present trial. The median age was 58 years. Most had received previous anthracycline (83%) and taxane (94%) therapy. The maximum tolerated dose was everolimus 7.5 mg daily and capecitabine 825 mg/m 2 . The incidence of grade 3 events was low and mainly hematologic in nature. One incident each of grade 4 neutropenia, thrombocytopenia, hyperglycemia, and mucositis occurred. No grade 5 events occurred. The clinical benefit rate was 50%. The median progression-free survival was 196 days, and the median overall survival was 569 days. Conclusion The all-oral regimen of everolimus with capecitabine is active and well tolerated, with encouraging results for progression-free survival, overall survival, and clinical benefit rate in patients with MBC.