The value of MR imaging in monitoring the effect of chemotherapy on bone sarcomas.

We studied the value of MR imaging in monitoring the response of Ewing sarcoma and osteosarcoma to chemotherapy. Relative signal-intensity changes on MR images in the course of chemotherapy were compared with changes in tumor volume and histopathologic findings. MR scans (T1- and T2-weighted spin-echo images) were obtained in 20 patients with bone sarcoma. The first MR scan was obtained before the administration of chemotherapy in all patients. The follow-up scan was obtained in the course of treatment, before surgery. Tumor-volume and signal-intensity measurements of the intra- and extraosseous components of the tumor were analyzed. In 17 patients, histopathologic findings of the resected tumor were available for comparison with the MR images. In 12 of 17 patients there was complete agreement between changes in tumor volume, changes in the signal intensity of the extraosseous tumor component on T2-weighted images, and histopathology. In another four cases, changes in signal intensity correlated either with histopathology or with changes in tumor volume. In one patient with a pathologic fracture, no such correlation existed. A significant correlation was found between changes in signal intensities and pathologic response (r = .57, p = .02), as well as between changes in tumor volume and pathologic response (r = .53, p = .03). No correlation could be found between changes in signal intensity of the intraosseous tumor component and changes in tumor volume or histopathology. We conclude that the signal intensity of the extraosseous component of bone sarcomas on T2-weighted MR images in addition to changes in tumor volume may be useful in evaluating response to chemotherapy.