INTRODUCTION: Radiation-associated sarcoma (RAS) is one of the most life-threatening complications associated with the treatment of malignant neoplasms. Because all RAS patients have a history of radiotherapy, there have been no effective treatment options when RAS is not completely resected. METHODS: We retrospectively reviewed 20 RAS patients, including 4 unresectable cases treated by carbon ion radiotherapy (CIRT). RESULTS: The primary diseases targeted by radiotherapy included malignant lymphoma (n = 4), cervical cancer (n = 3), pharyngeal cancer (n = 3), breast cancer (n = 2), lung cancer (n = 1), rectal cancer (n = 1), maxillary cancer (n = 1), synovial sarcoma (n = 1), and benign neoplasms (n = 4). The histological diagnoses of RAS included osteosarcoma (n = 8), leiomyosarcoma (n = 3), undifferentiated pleomorphic sarcoma (n = 3), rhabdomyosarcoma (n = 1), angiosarcoma (n = 1), malignant peripheral nerve sheath tumor (n = 1), spindle cell sarcoma NOS (n = 1), and sarcoma not further specified (n = 2). The median survival time from the diagnosis of RAS was 26 months. Eleven patients underwent surgery. Five of these patients achieved a continuous disease free (CDF) status or showed no evidence disease. Four patients underwent CIRT. One of these patients with leiomyosarcoma achieved a CDF status, and the other patient with osteosarcoma achieved a partial response. On the other hand, 2 patients experienced grade 3 toxicities that required surgical treatment. CONCLUSION: RAS originates from various types of diseases that are treated by radiotherapy and shows diverse pathological features. Complete resection achieves a good prognosis. CIRT can be an effective and feasible option for unresectable RAS.
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