Pazopanib maintenance therapy after tandem high-dose chemotherapy for disseminated Ewing sarcoma Abstract The dismal prognosis of patients with disseminated Ewing sarcoma necessitates the development of novel treatment strategies. Pazopanib is an oral multi-targeted tyrosine kinase inhibitor that is active against advanced soft tissue sarcoma. However, the clinical activity and feasibility of pazopanib for treating Ewing sarcoma remain poorly understood. Moreover, clinical information on the use of tandem high-dose chemotherapy for Ewing sarcoma is limited. A 14-year-old boy with Ewing sarcoma was transferred to our hospital for treatment. Magnetic resonance imaging, computed tomography scans, and bone scintigraphy revealed multiple lesions in the pubis, ilium, ischium, femur, rib, cranial bone, thoracic vertebrae, sacrum, obturator muscle, adductor magnus muscle, testicular cord, and lungs. Bone scintigraphy after intensive chemotherapies confirmed that multiple abnormal accumulations were still present in the cranial bone and pubis. Subsequently, the patient received tandem high-dose chemotherapy including topotecan, and radiotherapy. Abnormal accumulations have disappeared in bone scintigraphy. Subsequently, pazopanib maintenance therapy was initiated. Despite the presence of innumerable lesions at diagnosis, the patient has been in near-complete remission for the past 1 year with pazopanib administration. This confirms that adding pazopanib maintenance therapy after tandem high-dose chemotherapy is a therapeutic option for cases with disseminated Ewing sarcoma.