Ewing sarcoma: MR imaging of chemotherapy-induced changes with histologic correlation

Area of Science:

• Oncology
• Radiology
• Medical Imaging

Background:

• Ewing sarcoma is a rare bone cancer primarily affecting children and young adults.
• Accurate assessment of treatment response is crucial for patient management.
• Magnetic resonance (MR) imaging is a key modality for evaluating soft tissue tumors.

Purpose of the Study:

• To assess the signal intensity characteristics of Ewing sarcoma on MR images before and after chemotherapy.
• To determine the reliability of MR imaging in excluding active disease post-chemotherapy.
• To correlate MR imaging findings with histologic results.

Main Methods:

• Prospective study of 18 patients with biopsy-proven Ewing sarcoma.
• MR imaging performed at 1.5 T using standard spin-echo sequences (T1 and T2 weighted).
• Imaging conducted before and within 10 days after chemotherapy, with histologic correlation in 14 patients.

Main Results:

• Tumor visualized in 16/18 patients before chemotherapy.
• Post-chemotherapy MR images showed high T2-weighted signal intensity in areas of necrosis, hemorrhage, and repair.
• Viable tumor cells (microscopic) were found in both low and high signal intensity areas in 71% of patients.

Conclusions:

• MR imaging is unreliable for excluding active Ewing sarcoma after chemotherapy.
• Changes in signal intensity on MR images provide qualitative evidence of chemotherapeutic effect.
• Further research may be needed to improve MR imaging's accuracy in assessing treatment response.