Phase II study of pazopanib with oral topotecan in patients with metastatic and non-resectable soft tissue and bone sarcomas

Background: Pazopanib is active in refractory soft-tissue sarcoma (STS) and significantly prolongs PFS. Prior studies of combinations of metronomic topotecan with pazopanib have indicated preclinical evidence of response in patients with sarcoma. Methods: This prospective, single arm, phase II study evaluated the efficacy of the combination of pazopanib with topotecan in patients with metastatic or unresectable non-adipocytic STS. Furthermore, it incorporated exploratory arms for osteosarcoma and liposarcoma. The primary endpoint was progression-free rate at 12 weeks in the non-adipocytic STS cohort. Results: 57.5% of patients in the non-adipocytic STS cohort were progression free at 12 weeks, which did not meet the primary endpoint of the study (66%). The exploratory osteosarcoma cohort exceeded previously established phase II trial comparator data benchmark of 12% with a PFR at 12 weeks of 69.55%. Treatment with the combination of pazopanib and topotecan was accompanied by a grade 3 or 4 toxicities in most patients. Conclusions: In this prospective trial in refractory metastatic or unresectable STS and osteosarcoma, the combination of pazopanib with topotecan did not meet its primary endpoint of progression-free rate at 12 weeks. The combination of pazopanib with topotecan was associated with a high degree of toxicity.