Monitoring neovascularity as an indicator to response to chemotherapy in osteogenic and Ewing sarcoma using magnetic resonance angiography.

Histologic studies on resected specimen have shown that tumor neovascularity is related to prognosis and response to therapy in a variety of human neoplasms. In nine patients with osteogenic or Ewing sarcoma, we evaluated the use of magnetic resonance angiography (MRA) to assess neovascularity non-invasively in vivo and to monitor response to chemotherapy. Seven patients with osteosarcoma and two patients with Ewing sarcoma were studied before and after chemotherapy by MRA (2-D time-of-flight gradient-echo sequence, TR = 50 msec, TE = 9.5 msec, theta = 50 degrees, acquisition time 13 min). MR angiograms were assessed for chemotherapy-induced changes in neovascularity. MRA showed both feeder vessels and neovascularity. Six patients responded to chemotherapy ( > or = 90% histologic tumor necrosis). MRA demonstrated marked reduction in neovascularity in all responders. Three patients did not respond to chemotherapy ( < 90% histologic tumor necrosis). MRA demonstrated persistent or increased neovascularity in the non-responders. MRA provides a unique opportunity to study tumoral neovascularity noninvasively in vivo and helps to assess response to chemotherapy in patients with osteogenic or Ewing sarcoma. These general principles may be applicable to other human tumors.