Assessment of osteosarcoma response to neoadjuvant chemotherapy: comparative usefulness of dynamic gadolinium-enhanced spin-echo magnetic resonance imaging and technetium-99m skeletal angioscintigraphy.

The aim of this work was to study and compare the usefulness of dynamic contrast-enhanced spin-echo MR imaging with high temporal resolution hydroxymethylene diphosphonate technetium-99 m skeletal angioscintigraphy in predicting the osteosarcoma histological response to neoadjuvant chemotherapy. Twelve patients with resectable osteosarcoma were prospectively monitored with dynamic MR imaging and skeletal scintigraphy before start of neoadjuvant chemotherapy, after two cycles of therapy and before surgery. Neoplasm signal intensity and activity intensity were plotted against time, and slopes were calculated for percentage increase over baseline values in the first minute. Stability and increase in slope values during or after chemotherapy were defined as a "radiological non-response". Changes in slopes were compared with the "histological response" (Huvos grading). At midpoint of the chemotherapy, these two imaging modalities failed in predicting final histological response. After the completion of the chemotherapy, these imaging modalities allowed the prediction of histological response with the same accuracy (91 %). In this series, dynamic MR imaging and technetium skeletal scintigraphy provide similar results regarding the prediction of final histological response during neoadjuvant chemotherapy; these results cannot be used to modify the therapeutic protocol at midpoint of chemotherapy; these imaging tools predict accurately the histological response at the end of chemotherapy. These latter results may permit anticipation of the adjuvant chemotherapy strategy during decalcification procedures in resected osteosarcoma and thus to monitor chemotherapy in non-surgical osteosarcoma.