Molecular diagnostics play an increasing role in the diagnosis of Ewing sarcoma. The type of molecular testing used in clinical practice has been poorly described.


To describe patterns of translocation testing for newly diagnosed Ewing sarcoma.


Children's Oncology Group (COG) trial AEWS1221 was a phase III randomized trial enrolling patients with newly diagnosed metastatic Ewing sarcoma from 2014 to 2019. Patients were required to have a histologic diagnosis of Ewing sarcoma, but translocation testing was not required. Sites provided types and results of any molecular diagnostics performed.


Data from 305 enrolled patients were available. The most common type of molecular testing was fluorescence in situ hybridization (FISH) performed on the primary tumor (236 of 305 patients; 77.4%), with positive testing for an EWSR1 or FUS translocation in 211 (89.4%). Reverse transcription–polymerase chain reaction (RT-PCR) on the primary tumor was performed in 61 of 305 (20%), with positive results in 48 of 61 patients (78.7%). Next-generation sequencing was reported in 7 patients on primary tumor and in 3 patients on metastatic sites. Evaluating all types of testing on either primary or metastatic tumor, 16 of 305 patients (5.2%) had no reported translocation testing. Evaluating all results from all testing, 44 of 305 patients (14.4%) lacked documentation of an abnormality consistent with a molecular diagnosis of Ewing sarcoma.


COG sites enrolling in a Ewing sarcoma trial have high rates of testing by FISH or PCR. A small proportion of patients have no translocation testing on either primary or metastatic sites. Next-generation sequencing techniques are not yet commonly used in this context.

This content is only available as a PDF.

Author notes

Supplemental digital content is available for this article. See text for hyperlink.

AEWS1221 trial conduct was supported by NIH/NCI Grant U10 CA180899 (Children's Oncology Group Statistics and Data Center), the COG Foundation, NCTN Operations Center Grant U10CA180886, St. Baldrick's Foundation. Glade-Bender was supported by NIH/NCI CA008748.

DuBois has received fees for consulting and advisory board roles from Bayer and Loxo Oncology and has received travel expenses from Loxo Oncology, Roche/Genentech, and Salarius Pharmaceuticals. Lessnick is a Scientific Advisor to Salarius Pharmaceuticals and is listed as an inventor on patents related to NKZ2.2 and GSTM4 in Ewing sarcoma. The other authors have no relevant financial interest in the products or companies described in this article.

A preliminary version of this work was presented at the 2018 Connective Tissue Oncology Society Annual Meeting; November 14–17, 2018; Lisbon, Portugal.

Supplementary data