Adjuvant radiotherapy using intensity-modulated radiotherapy (IMRT) technique for localized extraskeletal osteosarcoma (ESOS): case report and literature review

Extraskeletal osteosarcoma (ESOS) is a rare mesenchymal malignancy. It is characterized by osteoid production without attachment to bone or periosteum. In contrast to conventional osteosarcoma, whose peak incidence is in the second decade, ESOS primarily affects adults in their fourth decades or older. Surgical resection is considered the mainstay treatment, but the relapse rate is high with unsatisfying prognosis. Due to its rarity, there is no universally accepted treatment algorithm for ESOS. Adjuvant radiotherapy (RT) in order to decrease local recurrence is considered. However, there is lack of studies demonstrating the dose, treatment field, technique, and adverse effects of RT in patients with ESOS. Here we report a 70-year-old man with ESOS at left thigh. The patient received tumor resection followed by adjuvant radiotherapy via modern intensity-modulated radiotherapy (IMRT) technique. The patient completed treatment course and maintained good limb function without devastating adverse effects. Current literatures regarding the clinical outcome and the debate of adjuvant treatment modalities are also reviewed.