Impact of Carbon Ion Radiotherapy on Inoperable Bone Sarcoma

SIMPLE SUMMARY: The standard treatment for bone sarcoma is surgery with or without additional chemotherapy; however, complete resection of the tumor might not be possible in patients with locally advanced lesions. Management of patients with bone sarcoma who are unsuitable for surgery is challenging. Carbon ion radiotherapy (C-ion RT) was initiated in 1994 for treating various cancers in Japan and is being considered to be an effective treatment for unresectable bone sarcoma. However, there is a limited number of reports on the clinical outcomes of C-ion RT for bone sarcoma. Here, we aimed to analyze the clinical outcomes and prognostic factors among patients with unresectable bone sarcoma who were treated with C-ion RT. We found that C-ion RT had favorable overall survival and local control with low toxicity rates compared to surgery. Therefore, our results suggest a potential role for C-ion RT in the radical treatment of inoperable bone sarcoma. ABSTRACT: Management of patients with bone sarcoma who are unsuitable for surgery is challenging. We aimed to analyze the clinical outcomes among such patients who were treated with carbon ion radiotherapy (C-ion RT). We reviewed the medical records of the patients treated with C-ion RT between April 2011 and February 2019 and analyzed the data of 53 patients. Toxicities were classified using the National Cancer Institute’s Common Terminology Criteria for Adverse Events (Version 4.0). The median follow-up duration for all patients was 36.9 months. Histologically, 32 patients had chordoma, 9 had chondrosarcoma, 8 had osteosarcoma, 3 had undifferentiated pleomorphic sarcoma, and 1 had sclerosing epithelioid fibrosarcoma. The estimated 3-year overall survival (OS), local control (LC), and progression-free survival (PFS) rates were 79.7%, 88.6%, and 68.9%, respectively. No patients developed grade 3 or higher acute toxicities. Three patients developed both grade 3 radiation dermatitis and osteomyelitis, one developed both grade 3 radiation dermatitis and soft tissue infection, and one developed rectum-sacrum-cutaneous fistula. C-ion RT showed favorable clinical outcomes in terms of OS, LC, and PFS and low rates of toxicity in bone sarcoma patients. These results suggest a potential role for C-ion RT in the management of this population.