Comparison of preparation regimens in patients undergoing autologous stem cell transplantation in terms of side effects and survival

Comparison of Preparation Regimens In Patients Undergoing Autologous Stem Cell Transplantation In Terms of Side Effects and Survival Objective: Autologous stem cell transplantation (ASCT) has become a standard approach used to improve treatment success, particularly in high-risk or relapsed pediatric solid tumors. This study aimed to evaluate the clinical outcomes, toxicity profiles, and prognostic factors affecting survival after ASCT in patients with neuroblastoma, Hodgkin lymphoma, and Ewing sarcoma. The effects of conditioning regimens, CD34+ cell dose, and disease status on survival were also investigated. Materials and Methods: A total of 43 patients (neuroblastoma = 22, Hodgkin lymphoma = 19, Ewing sarcoma = 2) who underwent autologous stem cell transplantation between 2000 and 2023 at the Pediatric Oncology Clinic of Çukurova University Faculty of Medicine were retrospectively evaluated. Patient demographics, pre-transplant disease status, conditioning regimens, CD34+ cell dose, engraftment times, post-transplant complications, and survival outcomes were obtained from archived files and electronic records. Survival analyses were performed using Kaplan-Meier and prognostic factors were evaluated using Cox regression. Findings: 51.2% of patients were still alive after transplantation. Median progression-free survival (PFS) was 20.5 months, and median overall survival (OS) was 70.4 months. Post-transplant relapse had a significantly negative impact on OS (p=0.038). A CD34+ cell dose above 3.3x106/kg was associated with longer survival (p=0.016). Patients undergoing transplantation with active disease had a significantly higher risk of mortality (p=0.024). The most common toxicities were febrile neutropenia (69.8%), upper respiratory tract infection (72.1%), electrolyte disturbances (72.1%), and gastrointestinal side effects (vomiting 67.4%, diarrhea 62.8%). Severe organ toxicities associated with mortality were rare. Among conditioning regimens, busulfan-based regimens were the most commonly used protocol (74.4%), and no statistical difference was found between regimen types and survival (p>0.05). Conclusion: This study demonstrates that prognosis after ASCT in pediatric solid tumors is particularly related to pre-transplant disease status, relapse rate, and CD34+ cell dose. While the incidence of high-dose chemotherapy-related toxicity is high, serious complications leading to mortality are limited. Pre-transplant disease control and adequate stem cell load are associated with improved survival. Our findings support the fact that autologous transplantation remains an effective treatment option for pediatric solid tumors with appropriate patient selection. Keywords: Autologous stem cell transplantation, pediatric solid tumor, neuroblastoma, Hodgkin lymphoma, Ewing sarcoma, CD34+, survival, toxicity.