PDGFRB and osteosarcoma: By inhibiting vascular endothelial growth factor receptor and PDGFR, pazopanib may improve the intratumoral delivery of chemotherapeutic agents during the “vascular normalization” phase, thereby enhancing the cytotoxic efficacy of chemotherapy.[14,15] This mechanism has been partially validated in studies of soft tissue sarcomas and other malignancies, suggesting that a similar effect may exist in osteosarcoma as well.