Single platform flow cytometric absolute CD34+ cell counts based on the ISHAGE guidelines. International Society of Hematotherapy and Graft Engineering

Impact of conditioning regimen on peripheral blood hematopoietic cell transplant

AIM

To investigate infused hematopoietic cell doses and their interaction with conditioning regimen intensity +/- total body irradiation (TBI) on outcomes after peripheral blood hematopoietic cell transplant (PBHCT).

METHODS

Our retrospective cohort included 247 patients receiving a first, T-replete, human leukocyte antigen-matched allogeneic PBHCT and treated between 2001 and 2012. Correlations were calculated using the Pearson product-moment correlation coefficient. Overall survival and progression free survival curves were generated using the Kaplan-Meier method and compared using the log-rank test.

RESULTS

Neutrophil engraftment was significantly faster after reduced intensity TBI based conditioning [reduced intensity conditioning (RIC) + TBI] and > 4 × 10⁶ CD34+ cells/kg infused. A higher total nucleated cell dose led to a higher incidence of grade II-IV acute graft-versus-host disease in the myeloablative + TBI regimen group (P = 0.03), but no significant difference in grade III-IV graft-versus-host disease. A higher total nucleated cell dose was also associated with increased incidence of moderate/severe chronic graft-versus-host disease, regardless of conditioning regimen. Overall and progression-free survival were significantly better in patients with a RIC + TBI regimen and total nucleated cell dose > 8 × 10⁸/kg (3 years, overall survival: 70% vs 38%, P = 0.02, 3 years, progression free survival: 64% vs 38%, P = 0.02).

CONCLUSION

TBI and conditioning intensity may alter the relationship between infused cell doses and outcomes after PBHCT. Immune cell subsets may predict improved survival after unmanipulated PBHCT.