Complication rate, functional outcomes, and risk factors associated with carbon ion radiotherapy for patients with unresectable pelvic bone sarcoma

Background To the authors' knowledge, carbon ion radiotherapy (CIRT) is one of the few curative treatments for unresectable pelvic bone sarcoma. The current study investigated the complications, functional outcomes, and risk factors of CIRT. Methods Of 112 patients who were treated with CIRT for unresectable pelvic bone sarcoma, the authors enrolled 29 patients who were without local disease recurrence or distant metastasis. The mean follow‐up was 93 months. Complications, functional outcomes, and quality of life scores were assessed. Risk factors were analyzed, including the dose‐volume histogram of the femoral head. Results Femoral head necrosis occurred in approximately 37% of patients, pelvic fractures were reported in 48% of patients, and neurological deficits were noted in 52% of patients. Femoral head necrosis was found to be significantly more prevalent among patients with periacetabular tumors (P = .018). The dose‐volume histogram of the femoral head indicated tolerable volume percentages of the femoral head to be 50 years and those with periacetabular tumors were found to have significantly lower Toronto Extremity Salvage Scores. Conclusions Femoral head necrosis, pelvic fracture, and nerve damage are common complications with the use of CIRT for pelvic bone sarcoma. To prevent femoral head necrosis, the radiation dose to the femoral head should be kept below the estimated tolerance curve presented in the current study. The functional outcome is nearly equivalent to that of surgery. CIRT may be a promising alternative to surgery for patients with unresectable pelvic bone sarcoma. The functional outcome of carbon ion radiotherapy for patients with inoperable pelvic bone tumors is nearly equivalent to that of surgery. The radiation dose to the femoral head should be kept below the estimated tolerance curve presented herein to prevent femoral head necrosis.