2350 - Treatment Approach in Childhood Ewing Sarcoma - TROD Hematology Oncology Pediatric Oncology Total Body Irradiation Working Group Survey Study

Purpose/Objective(s): This study aimed to determine the variations in treatment approaches for childhood Ewing's sarcoma among different centers in our country.

Materials/Methods: For this purpose, a survey was prepared via SurveyMonkey and distributed to members through the Turkish Society for Radiation Oncology. Eleven centers that responded to the survey were included in the study, and the results were analyzed.

Results: Among the 11 centers participating in the survey, 9 centers (81.8%) reported administering radiotherapy (RT) to 0–10 patients, 1 center (9.1%) 11–20 patients, and 1 center (9.1%) more than 20 patients per year. Regarding treatment protocols, 8 centers (72.7%) followed the SIOPE Euro-Ewing protocol, while 3 centers (27.3%) followed the COG AEWS0031 protocol. The most common tumor location at diagnosis was the extremities in 8 centers (72.7%) and the pelvis in 3 centers (27.3%). When evaluating the decision for adjuvant RT based on surgical margin status, 5 centers (45.5%) recommended adjuvant RT even with negative surgical margins, while 6 centers (54.5%) found it unnecessary. All centers reported using a postoperative RT dose of 45–56 Gy. For definitive RT, a dose of 50–56 Gy, 57–60 Gy, and 61–66 Gy were prescribed in 1 center (9.1%), 6 centers (54.5%), and 4 centers (36.4%), respectively. Regarding GTV-CTV margin expansion, 6 centers (54.5%) used 5–10 mm, 4 centers (36.4%) used 11–15 mm, and 1 center (9.1%) used 16–20 mm. In terms of RT techniques, 3D conformal RT, IMRT, and VMAT were used by 5 centers (45.4%), 2 centers (18.2%), and 4 centers (36.4%), respectively. For metastatic pediatric Ewing's sarcoma, 4 centers’ (36.4%) approach was palliative, while 7 centers (63.6%) provided curative treatment. The palliative RT dose-fractionation schemes varied among centers: 30 Gy / 10 fractions in 4 centers (36.4%), 30 Gy in 10 fractions or 40 Gy in 5 fractions in 1 center (9.1%), 36 Gy in 12 fractions in 1 center (9.1%), and 25 Gy in 10 fractions in 1 center (9.1%). In the management of distant metastases, SBRT was used in 8 centers (72.7%), while 3 centers (27.3%) preferred conventional fractionation techniques. Prophylactic bilateral lung RT was administered in 7 centers (64%) with initial lung metastases who achieved a complete response to chemotherapy. Adjuvant RT decisions based on the degree of tumor necrosis in the surgical specimen after chemotherapy, responses were received from 9 centers. Five centers (55.6%) applied adjuvant RT for 0–50% necrosis and 2 centers (22.2%) applied for 51–99% necrosis. Two centers (22.2%) did not consider necrosis percentage in the decision regarding adjuvant RT.

Conclusion: The differences in adjuvant RT indications and techniques between the two main international protocols used for treating childhood Ewing's sarcoma in our country seem to partially explain the variability in treatment approaches across the centers. In the radiotherapy of pediatric tumor patients, it is crucial to adhere as closely as possible to the specific treatment protocol being followed.