重粒子線治療を行った仙骨原発線維肉腫の1例

Primary Fibrosarcoma of the Sacrum Treated with Carbon-ion Radiotherapy. Case Report

　症例は25歳の女性で，1年前から右腰殿部痛があった．単純X線像上，仙骨右外側部に地図状の骨透亮像を認め，単純CTでは，骨溶解像の周囲に不規則な辺縁硬化像を認めた．単純MRIでは，T1・T2強調像ともに低信号で，脊柱管内への進展が認められた．針生検組織で，線維肉腫と診断された．重粒子線治療を選択し，線量70.4GyEを照射した．照射後2年の現在，疼痛は消失し，ADL障害はない．重粒子線治療は，切除非適応症例だけでなく，切除に伴う機能損失が極めて大きい症例に対しても，切除に代わりうる可能性がある．

　We report a rare case of primary fibrosarcoma of the sacrum treated with carbon-ion radiotherapy. The patient was a 25-year-old woman who had a 1-year history of pain in the sacral region. Radiographic examination revealed a geographic osteolytic lesion having a trabeculated appearance in the lateral part of the sacrum. CT showed a purely osteolytic lesion with a thin sclerotic margin. On MRI the lesion was homogeneously low signal on both the T1-weighted and T2-weighted images, and it had extended into the spinal canal. Examination of a needle biopsy specimen yielded a pathological diagnosis of fibrosarcoma. The patient was treated with carbon-ion radiotherapy at a dose of 70.4 GyE. As of two years after treatment, the patient is pain-free, and there are no impairments of activities of daily living. Carbon-ion radiotherapy seems to be a promising alternative to surgery for the management not only patients of with unresectable tumors but of patients in whom tumor resection is predicted to result in severe loss of function.