Tc-99m MIBI to evaluate children with Ewing's sarcoma

Purpose: Tc-99m MIBI has been used increasingly to evaluate benign and mali gnant tumors because of its tumor-seeking properties and ability to provide an imaging assessment of multiple-drug resistance. This study investigated the clinical utility of Tc-99m MIBI in the management of Ewing's sarcoma i n children. Methods: Thirteen Tc-99m MIBI studies in nine (six male, three female) pati ents ages 6.5 to 20 years (mean, 13.4 years) with Ewing's sarcoma were revi ewed. All patients had imaging studies at diagnosis, and four had follow-up studies during or after therapy, Scintigraphy was evaluated for Tc-99m MIB I uptake within the tumor and in metastases, which other imaging modalities had shown to be present in four patients. Scintigraphic results were corre lated with the clinical course in all patients and with tumor P-glycoprotei n status in six patients. Results: Tc-99m MIBI accumulated in 6 of 9 primary tumors and did not accum ulate in one recurrent tumor. No metastases showed Tc-99m MIBI uptake. The presence or absence of Tc-99m MIBI uptake at diagnosis or after therapy car ried no prognostic significance. Tc-99m MIBI was present in the two tumors that were P-glycoprotein positive and in only one of four tumors that were P-glycoprotein negative. Conclusion: Tc-99m MIBI imaging does not appear to be useful in Ewing's sar coma.