OBJECTIVETo evaluate the CT features of radiation-induced jaw osteosarcoma(RIJOS) developed after therapeutic irradiation for a variety of nonosseous lesions.

METHODSThe demographic and CT findings of thirteen patients with RIJOS were reviewed retrospectively.Observation items included location, bone destruction, mineralized tumor matrix, periosteal reaction, soft tissue extension and calcification.Of the thirteen patients, twelve were male and one was female. The mean age was 48 years (range: 29-68 years).Five patients had tumors in the maxilla and eight in the mandible. All the patients underwent tumor resection.

RESULTSThe latent period before development of RIJOS ranged from 3.5 to 14 years (mean, 11 years).In all thirteen patients, eight tumors were osteoblastic, with one osteolytic and four mixed lesions.Osteoid tumor matrix mineralization was present in twelve patients. Periosteal reaction was identified in 11 cases.Soft-tissue extension was present in all patients beyond the area of bone destruction.

CONCLUSIONSThe characteristic CT imaging of RIJOS showed the bone destruction associated with a large number of mineralized tumor matrix and significant soft tissue extension in the original radiation field after radiotherapy. CT findings could play an important role in identifying the tumor and pre-operative assessment.