Methods
Oral cabozantinib (25mg/m2) was administered daily for 21 (dose level 1) or 14 (dose level -1B) days. Topotecan (0.75mg/m2) and cyclophosphamide (250mg/m2) were administered IV on days 1-5. A modified 3+3 design based upon first cycle dose-limiting toxicities (DLT) was used for dose escalation.