[Osteosarcoma: magnetic resonance imaging of the effects of preoperative chemotherapy].

The effects of preoperative chemotherapy for osteosarcoma of the extremities were investigated with MR imaging. Forty-six patients affected with high-grade osteosarcomas of the extremities underwent MRI before and after two cycles of preoperative chemotherapy. At the end of treatment all tumors were resected and the rate of tumor necrosis was assessed on histologic sections. The MR images obtained before and after treatment were compared. Decreased tumor size, perilesional intramedullary edema and more marked lesion outline correlated well with positive histologic response to preoperative chemotherapy. Soft tissue edema and joint effusion did not change significantly and no clear correlation with histologic response was observed. Decreased signal intensity on T2-weighted images is likely to indicate response to chemotherapy. Likewise, poor response correlated with unchanged/increased signal intensity. Therefore, MRI appears a useful means to evaluate chemotherapy-induced changes in osteosarcomas of the extremities.