Impact of CD34 positive cell dose in donor graft on the outcomes after haploidentical peripheral blood stem cell transplantation with post-transplant cyclophosphamide – A retrospective single-center study with a Japanese cohort

Background

Haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) with post-transplant cyclophosphamide (PTCy) is an important therapeutic option for patients lacking an HLA-matched donor. However, the significance of CD34⁺ cell dose in grafts has not been fully elucidated.

Objective

We aimed to explore the impact of CD34⁺ cell dose on outcomes after haplo-PBSCT with PTCy.

Study Design

We retrospectively investigated 111 consecutive patients who underwent haplo-PBSCT with PTCy or HLA-matched PBSCT from related donors.

Results

There were no statistically significant differences in 3-year overall survival (p = 0.559) or progression-free survival (p = 0.974) between haplo-PBSCT and matched PBSCT. Delayed neutrophil engraftment and a lower incidence of graft-versus-host disease were observed in haplo-PBSCT. The median dose of CD34⁺ cells was 4.9 × 10⁶ /kg in 57 haplo-PBSCT and 4.5 × 10⁶ /kg in 54 matched PBSCTs. Importantly, patients who underwent haplo-PBSCT with the administration of CD34⁺ cell at a dose of ≥4.0 × 10⁶ /kg significantly had improved OS (p = 0.015) and decreased incidence of disease relapse (p = 0.001) without increasing incidence of GVHD.

Conclusion

Our data suggest that a higher dose of CD34⁺ cells in haplo-PBSCT with PTCy positively impacts the outcomes without an increase of GVHD.