Impact of CD34+ cell dose on outcomes of related allogeneic PBSCT in adult AML patients.

CD34+ cell dose is believed to impact the outcomes of allogeneic peripheral blood stem cell transplantation (PBSCT), yet the optimal dose remains unclear. We retrospectively reviewed 2407 adult patients with acute myeloid leukaemia who underwent their first related PBSCT between 2000 and 2019. The median infused CD34+ cell dose was 3.67 × 106/kg. Patients were divided into three groups based on infused CD34+ cell dose: low (1.0-2.0 × 106/kg), intermediate (2.0-4.0 × 106/kg) and high (4.0-10.0 × 106/kg) groups. The 5-year overall survival rates were 37.2%, 40.2% and 37.4% in the low, intermediate and high groups respectively (p = 0.176). Although the high-group patients experienced faster neutrophil engraftment, cumulative incidences of infection and primary engraftment failure were comparable across groups. Platelet engraftment was significantly delayed in the low group, with 21.7% failing to engraft at day 100, compared to 14.6% and 13.4% in the intermediate and high groups (p < 0.001). Furthermore, the incidence of secondary graft failure was significantly higher in the low group. In conclusion, a CD34+ cell dose >2.0 × 106/kg improves platelet engraftment and reduces the risk of secondary graft failure but does not confer additional long-term benefits.