Abstract
Undifferentiated pleomorphic sarcoma (UPS) is a high-grade, aggressive soft tissue sarcoma (STS) with a poor prognosis, and no definitive or effective treatment is currently available for it. Pazopanib, an orally available multiple tyrosine kinase inhibitor, has been approved for the treatment of advanced STS. The present study documents the case of a 51-year-old man with advanced UPS with coamplification of platelet-derived growth factor receptor A (PDGFRA), vascular endothelial growth factor receptor 2 (VEGFR2) and stem cell factor receptor (KIT) genes. The patient exhibited a marked and sustained response to pazopanib. The patient presented with a retroperitoneal tumour with pancreatic head lymph node metastasis, and bone metastases in the second/fifth thoracic vertebrae and left femur. Based on the histological analysis of the retroperitoneal tumour and femoral mass, the patient was diagnosed with UPS. Palliative radiation therapy was administered to the left femur and second/fifth thoracic vertebrae to prevent fractures. After radiation therapy, the patient achieved a partial response after eight courses of doxorubicin. A comprehensive genomic profiling analysis (FoundationOne(®) CDx) revealed coamplification of PDGFRA, VEGFR2 and KIT genes. Hence, pazopanib was initiated as a second-line treatment. Notably, the retroperitoneal tumour shrank, and no new lesions developed for 3 years after the initiation of pazopanib treatment. This response suggests that the coamplification of PDGFRA, VEGFR2 and KIT may predict favourable outcomes in response to pazopanib.