Haploidentical Peripheral Blood Allografts with PTCy for Pediatric Blood Cancers

According to a single-center study, haploidentical peripheral blood stem cell (PBSC) allografts with post-transplant cyclophosphamide (PTCy) demonstrated comparable outcomes for treating pediatric blood cancers relative to matched sibling or unrelated donor bone marrow allografts. These findings were published in Transplantation and Cellular Therapy.

“Introduction of PTCy as graft-versus-host disease (GVHD) prophylaxis has made haploidentical hematopoietic stem cell transplantation (HSCT) a common approach in adults, but pediatric experience is limited,” wrote the study authors. “Based on the encouraging adult data and to decrease the risk of graft failure, our center has increasingly used PBSCs from haploidentical donors utilizing PTCy.”

In a retrospective analysis, the researchers analyzed 104 pediatric patients who underwent allogeneic HSCT for a hematological malignancy or myelodysplastic syndrome between January 2014 and December 2020. Patients received an allograft from either a haploidentical family donor (n = 26), a matched sibling donor (n = 31), or a matched unrelated donor (n = 47). The primary endpoint was incidence of GVHD-free relapse-free survival (GRFS), and secondary endpoints included overall survival (OS), relapse-free survival (RFS), non-relapse mortality (NRM), and incidence of acute or chronic GVHD. Median follow-up was 573 days.

The researchers reported comparable between-group incidence of acute GVHD; however, chronic GVHD at 18 months was more common with matched unrelated donor allografts (31.7%) compared with matched sibling donors (10.0%), and haploidentical PBSC (9.2%; all P = 0.02). Cumulative incidences of relapse or NRM were similar overall at 18 months.

At 18 months, OS and RFS were 80.7% and 73.8% for the haploidentical group, 83.4% and 70.3% for the matched unrelated donor group, and 80.9% and 66.5% for matched sibling group, respectively. Between-group differences in OS and RFS were not statistically significant. GRFS was 61% in the haploidentical group, 44.6% for the matched unrelated donor group, and 62.1% for the matched sibling group (P = 0.26).

In summary, the authors wrote, “Haploidentical PBSC transplants with PTCy had comparable outcomes to MSD and MUD bone marrow and less chronic GVHD compared to MUD bone marrow in children. The logistical advantages and lower resource burden of haploidentical transplants with PBSC make it a feasible alternative to MUD donors in children with hematological malignancies. Given that this is a retrospective comparison of transplantation platforms rather than donor types, further prospective studies are warranted.”