Efficacy of pazopanib monotherapy in patients who had been heavily pretreated for metastatic soft tissue sarcoma: A retrospective case series

Background: We retrospectively reviewed outcomes of treatment with pazopanib, an oral multi-tyrosine kinase angiogenesis inhibitor, in patients with advanced soft tissue sarcoma, a rare and heterogeneous tumor group with limited treatment options. Methods: Between 2009 and 2013, 43 patients with metastatic soft tissue sarcoma received pazopanib as salvage chemotherapy after one or more cytotoxic regimens. Response rate, progression-free survival, and overall survival were analyzed according to histological subtype, Eastern Cooperative Oncology Group performance status, and metastatic site. Results: Common histological subtypes included leiomyosarcoma (n = 9), angiosarcoma (n = 6), malignant fibrous histiocytoma/undifferentiated pleomorphic sarcoma (MFH/UPS, n = 5), malignant peripheral nerve sheath tumor (MPNST, n = 5), and synovial sarcoma (n = 4). Nineteen patients (44.2%) received more than two chemotherapy regimens before pazopanib. At the time of analysis, 208 treatment cycles of pazopanib had been administered (median, 4.8 cycles per patient), and no treatment-related mortality occurred. The disease control rate was 61.0% (95% confidence interval [CI], 46.1-75.9%), and the overall response rate was 17.1% (partial response, n = 7; complete response, n = 0). Partial response was achieved in two patients with synovial sarcoma, two with MFH/UPS, one with MPNST, one with leiomyosarcoma, and one with angiosarcoma. The median lengths of progression-free survival and overall survival were 5.0 months (95% CI, 3.6-6.4 months) and 8.2 months (95% CI, 5.8-10.6 months), respectively. Progression-free survival was shorter in the patients with liposarcoma and rhabdomyosarcoma (1.3 and 0.9 months, respectively) than in those with leiomyosarcoma, MPNST, MFH/UPS, and synovial sarcoma (5.6, 6.5, 7.1, and 7.7 months, respectively). Conclusions: Pazopanib demonstrated acceptable antitumor activity in the Asian patients who had been heavily pretreated for sarcoma, with seemingly more favorable results in the patients with leiomyosarcoma, MPNST, MFH/UPS, and synovial sarcoma than in those with liposarcoma and rhabdomyosarcoma.