Engraftment Kinetics and Outcomes in Haploidentical Bone Marrow Transplantation Using Low-Dose Post-Transplant Cyclophosphamide : An Observational Follow-Up Study

In the literature, Haploidentical hematopoietic stem cell transplantation (HSCT) is increasingly utilized for patients lacking fully matched donors, but it carries risks of graft-versus-host disease (GVHD) and infections. Low-dose post-transplant cyclophosphamide (PTCy) may optimize engraftment kinetics while minimizing complications. This study evaluated the impact of low-dose PTCy on engraftment, GVHD, infection rates, and hospital stay in haploidentical HSCT. Methods: An observational follow-up study was conducted at the Maadi Armed Forces Medical Compound, Egypt, from January 2020 to March 2024, including 40 patients undergoing haploidentical HSCT with low-dose PTCy (25–30 mg/kg). Patients aged 10–60 years with hematological diseases were included. Engraftment kinetics, infection rates, GVHD incidence, and hospital stay were assessed via daily complete blood counts, chimerism studies, and clinical evaluations. Results: Neutrophil engraftment occurred at a median of 13 days, with 92% achieving full donor chimerism by day 30. Platelet engraftment averaged 23–28 days. Pre-engraftment fever occurred in 75% (25 mg/kg) and 96.4% (30 mg/kg) of patients, with bloodstream infections in 41.7% and 53.6%, respectively. GVHD incidence (grades I–IV) was 33–60% (25 mg/kg) and 21.4–60% (30 mg/kg). Sepsis-related mortality was 5%. Average hospital stay was 16 ± 1 days. Conclusion: Low-dose PTCy promotes rapid engraftment and reduces GVHD and infection-related mortality, offering a viable strategy for haploidentical HSCT, particularly in resource-limited settings.