RETROSPECTIVE ANALYSIS OF CHIMERISM ON PEDIATRIC PATIENTS WITH LEUKEMIA POST ALLOGENEIC STEM CELL TRANSPLANT

Abstract

Introduction: Allogeneic Stem Cell Transplant (ASCT) is a curative strategy for varioushematological diseases. Following ASCT, chimerism analysis becomes instrumental inassessing engraftment success, guiding immunosuppression strategies, anddetermining the necessity of interventions such as Donor Lymphocyte Infusion (DLI). Inleukemia cases, chimerism evaluation is a crucial tool for predicting and monitoringdisease relapse. However, the routine chimerism and its efficacy in the pediatricpopulation remain subjects of ongoing debate, necessitating further studies. Objective: Assess the correlation between chimerism levels, timing of testing, and their predictivevalue for disease relapse and survival among pediatric patients with leukemiapost-ASCT. Materials and methods: This retrospective study enrolled pediatric patientsdiagnosed with leukemia who underwent ASCT. Patients with other hematologicaldiseases and those who received autologous stem cell transplants were excluded fromthe analysis. This retrospective study was conducted in a tertiary care center, and thedata was collected from 2021 until January 2024. Demographic characteristics, survival,and clinical/laboratory findings, including chimerism analysis of 1-year after ASCT viaimmunophenotyping using flow cytometry. The Chimerism analysis was performed at sixcheckpoints (D+30, D+60, D+100, six months, nine months, and 12 months). Thestatistical analysis was made using descriptive statistics. Results: Of the 90 patients cohort, 85 (94%) patients underwent a single transplant, while 5 (6%) patients had twobone marrow transplants. Among the patients who achieved successful engraftment, 19 (21%) experienced disease relapse, with 9 relapses occurring within the first yearpost-ASCT. Notably, all relapses between D+100 and 12-months post transplantoccurred in patients with complete chimerism. The 9-month checkpoint exhibited thelowest patient attendance, with only 44% of patients having complete chimerism dataand 36 missing results. Conversely, the D+60 checkpoint had the fewest missing tests,with only 13 absences. The initial three checkpoints (D+30, D+60, D+100) demonstrated higher attendance rates than later. The majority of deaths occurred duringthe D+100 period, with 6 out of 9 relapses occurring during this timeframe. It was alsothe period with the higher percentage of mixed chimerism, having 22% in the D+30, 21% in the D+60, and 17% in the D+100. Conclusion: Overall, these findings suggestthat chimerism analysis, particularly at critical time points such as D+100, is valuable tohelp predict disease relapse in pediatric patients post-transplant and their survival.However, challenges in patient attendance at certain checkpoints indicate the need forimproved monitoring strategies to optimize patient outcomes.