Phase II study of sunitinib malate, a multitargeted tyrosine kinase inhibitor in patients with relapsed or refractory soft tissue sarcomas. Focus on three prevalent histologies: Leiomyosarcoma, liposarcoma and malignant fibrous histiocytoma

Soft tissue sarcomas (STS) represent a diverse group of histologic subtypes with targetable molecular alterations, often treated as a single disease. Sunitinib malate is a multitargeted receptor tyrosine kinase inhibitor active in other solid tumors carrying similar alterations (i.e., imatinib mesylate-refractory gastrointestinal stromal tumors). This single-institution phase II study investigated the safety and efficacy of sunitinib malate in three common STS subtypes. Patients with documented unresectable or metastatic STS (liposarcoma, leiomyosarcoma and malignant fibrous histiocytoma [MFH]), measurable disease, and 3 or less prior lines of therapy were eligible. Treatment consisted of sunitinib malate, 50 mg daily, for 4 weeks every 6 weeks. Forty-eight patients were enrolled, and 35% were heavily pretreated (≥2 prior lines of chemotherapy). The safety profile resembled previously known sunitinib malate toxicities. Median progression-free and overall survivals for liposarcoma, leiomyosarcoma, and MFH were 3.9 and 18.6, 4.2 and 10.1 and 2.5 and 13.6 months, respectively. The 3-month progression-free rates in the untreated and pretreated (chemotherapy) patients with liposarcoma, leiomyosarcoma and MFH were 75% and 69.2%, 60%, and 62.5% and 25% and 44.4%, respectively. With the caveats that a minority of patients with potentially indolent or low-grade disease could have been included and the small numbers, a 3-month progression-free rate of >40% suggests activity for sunitinib malate at least in liposarcomas and leiomyosarcomas. Thus, we believe that further investigation in these susceptible STS subtypes is warranted.