1238 Available online at www.medicinescience.org ORIGINAL ARTICLE Medicine Science 2022;11(3):1238-41 Efcacy of High Dose Chemotherapy in Adult Patients with Relapsed or Refractory Ewing Sarcoma Musa Baris Aykan, Gul Sema Keskin, Ece Ornek, Alper Topal, Caglar Koseoglu, Aysegul Dumludag, Ismail Erturk, Nuri Karadurmus Ankara Gülhane Faculty of Medicine, Department of Oncology, Ankara Turkey Received 04 May 2022; Accepted 22 July 2022 Available online 25.08.2022 with doi: 10.5455/medscience.2022.05.106 Copyright@Author(s) - Available online at www.medicinescience.org Content of this journal is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. Abstract A rare condition in adults, Ewing sarcoma (EWS) has no standard treatment during the relapse–refractory period. In our study, we aimed to identify the treatment-related side efects of high-dose chemotherapy (HDC) and salvage autologous stem cell transplantation (ASCT) in adult patients with relapsed or refractory EWS and their sur- vival rates. In a retrospective study, we recorded the clinical characteristics of patients with relapsed or refractory EWS treated with HDC in the hospital’s patient registry to determine their objective response rate (ORR), progression-free survival (PFS), 6-month PFS rate, overall survival (OS), 6-month OS rate, transplantation-related mor- tality (TRM) and treatment-related side efects. In our sample of 29 patients (72.4% male), the mean age was 26.41 years (SD=9.35). The most common primary tumour site was the lower extremities (31%), 69% of patients had lung metastases, and 48.1% had undergone surgical resection, adjuvant radiotherapy and chemotherapy. The ORR to HDC was 31%. Median PFS (IQR) was 5.35 (6.79) months (95% confdence interval =4.23–8.28), whereas the 6-month PFS rate was 38.9%. Median OS (IQR) was 9.46 (14.45) months (95% confdence interval = 8.52–15.82), whereas the 6-month OS rate was 68.1%. Mortality from HDC or other causes occurred in fve patients within the frst 100 days after ASCT. Grade 3 febrile neutropenia and thrombocytopenia were present in all patients until engraftment following ASCT. Amongst adults with relapsed or refractory EWS, HDC has successful survival and response rates and a manageable side-efects profle Keywords: Ewing sarcoma, high-dose chemotherapy, autologous stem cell transplantation Introduction While sarcomas represent less than 1% of all malignancies in adults, approximately 15% of sarcomas are bone sarcomas (1,2), amongst which Ewing sarcoma (EWS) is the most frequently observed. A malignancy that often originates from bone and soft tissue (3), EWS is more common in children and young adults than in adults. Although current treatments for local EWS have survival rates exceeding 70% (4,5), survival rates for relapsed or refractory EWS are not as high. In fact, the 3-year survival rate for patients who are metastatic at diagnosis and treated according to conventional chemotherapy protocols is 10–30% (5,6). The survival rates for patients with relapsed or refractory EWS are even worse despite combined systemic treatments, with a 5-year survival rate following frst-line therapy of less than 20% (6,7). Moreover, given the lack of standard treatment for patients with relapsed or refractory EWS, adults with such EWS represent a patient group whose treatment needs remain unmet. High-dose chemotherapy (HDC) followed by salvage autologous stem cell transplantation (ASCT) is frequently used to treat haematological and various solid malignancies. With a treatment rationale based on elevating responses by increasing the dosage in chemosensitive tumours, the method achieves successful survival responses against many malignancies, including lymphomas, multiple myeloma and germ cell tumours (8,9). Beyond that, the myelotoxicity-related side efects of HDC can be eliminated when coupled with salvage ASCT. Amongst patients with EWS, HDC is a treatment modality whose role has been investigated mostly retrospectively, frequently with regimens containing busulfan and melphalan (10,11), which have diferent severe side efects as well as risk myelotoxicity. By contrast, studies on systemic treatments for EWS with more manageable toxicity have been rare. Meanwhile, the efcacy of chemotherapy combining ifosfamide, carboplatin and etoposide (ICE) has been demonstrated in numerous *Corresponding Author: Musa Baris Aykan, Ankara Gülhane Faculty of Medicine, Department of Oncology, Ankara Turkey E-mail: musabarisaykan@gmail.com Medicine Science International Medical Journal