Utility of bone marrow aspiration and biopsy in initial staging of Ewing sarcoma

Background: The current standard of care for initial staging of pediatric Ewing sarcoma (EWS) patients is to obtain a bilateral bone marrow aspiration and biopsy (BMAB). The incidence of bone marrow (BM) disease in patients deemed non-metastatic by conventional and metabolic imaging and the concordance of BM positivity with other clinical characteristics are not well established. Procedure: This study is a multi-institutional retrospective review of newly diagnosed EWS patients less than 40 years of age with initial staging that included imaging and BMAB. Results: A total of 116 patients were eligible with 85 patients considered non-metastatic and 31 considered metastatic by imaging. None of the 85 patients with non-metastatic disease were BMAB positive (0%; 95% CI: 0-4.2%); 13 of the 31 patients with metastases were BMAB positive (41.9%; 95% CI: 24.5-60.9%). Primary tumor size was significantly higher in patients with metastases (P=0.017). Bone metastasis by imaging had high correlation with BMAB positivity (P=0.0002). In addition, the number of bony metastatic sites was significantly higher in patients with a positive BMAB as compared to those with a negative BMAB (median 3.5 and 0.0, respectively; P<0.001). Conclusions: BMAB may not be required for initial staging of pediatric and young adult EWS patients deemed non-metastatic by imaging. In patients with metastatic disease, there is a high correlation of BM involvement with multiple bone metastases.