Pelvic Ewing sarcoma in children: Multimodal treatment, long term outcome and prognostic factors.

Abstract

e22010 Background: The pelvis is one of the primary sites of Ewing sarcoma (ES) and is associated with a higher rate of local recurrence and poorer prognosis, compared with nonpelvic sites. Due to the rarity of this disease and limited data available, the prognostic factors of pelvic ES remain controversial. This study aims to assess the demographic, clinical features, treatment approach, outcome and prognostic factors in children with pelvic Ewing Sarcoma. Methods: Files of 264 children and adolescents with Ewing sarcoma diagnosed and treated between 1990-2022 in our center were retrospectively reviewed, of these 42 (15.9 %) were located in the pelvis. All recieved a COG modified chemotherapy regimen of ifosfamide-etoposide, alternating with vincristin, adriamisin/actinomycinD and cyclophosphamide (IE/VAC) every three weeks (every two weeks since 2012). Local treatment was discussed in each patient in the tumor board. Variables including age, gender, tumor stage, local and systemic treatment, outcome were analyzed using the Kaplan-Meier method and log rank test. Results: The median age of the 42 (23 male, 19 female) patients was 12.5 (2-16) years. The median time to diagnosis was 4 (0.25-12) months. The primary site was skeletal in 37 and extraskeletal in 5 patients. Seventeen (%40) had metastasis at diagnosis (lung, bone, bone marrow). Radiotherapy (RT) was given to 36 patients (10 preoperatively, 5 postoperatively, 21 definitive RT), 19 underwent surgery (4 at diagnosis, 14 had additional RT ). Surgical margins were positive in 6 and negative in 13. The histopathological necrosis was <90% in 6 and ≥ 90% in 9. The median follow-up was 56 (10-370) months. At a median of 13 months (3-115), 22 patients had recurrence(9) /progression (13). The 3-year event free survival (EFS) and overall survival (OS) were 50.1% and 62.6%; in all; 62.2 and 75.3% in nonmetastatic; 31.9% ve %42.9% in metastatic patients ( p=0.048, p= 0.028) respectively. The 3-year EFS and OS were significantly higher in patients with negative surgical margins compared to ones with positive margins [(%83.9 vs 0 % (p=0.0001) and %91.7 vs %16.7 (p=0.001) respectively] . The 3-year EFS and overall survival OS were higher in patients with ≥90% necrosis [76.2 vs 33.3 % ( p=0.029); 87.5 vs 50% (p=0.13)respectively]. Age, gender, the mode of local therapy (surgery/RT/RT+surgery) was not prognostic. One patient who had recieved oral etoposide and RT at recurrence and who achieved a complete response, developed acute myeloid leukemia (AML), M5 myelomonocytic subtype, 20 months after relapse, and died. Conclusions: In our cohort of patients with pelvic Ewing sarcoma, 40% had metastasis at diagnosis. Metastasis, positive surgical margins, poor necrosois rate <90% after neoadjuvant chemotherapy were found to be poor prognostic factors for outcome. Patients with localized pelvic Ewing sarcoma had a successful outcome with multidisciplinary treatment approach.