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Haploidentical donor HSCT may confer similar outcomes to matched, related donors
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Haploidentical stem cell transplantation recipients may achieve similar early immune recovery and clinical outcomes as patients undergoing allogeneic hematopoietic stem cell transplantation with HLA-matched donors, according to the results of a retrospective study.
Allogeneic hematopoietic stem cell transplantation (HSCT) is potentially curative for patients with hematologic malignancies. Although haploidentical donor transplantation is an available options for patients who lack a matched related donor, it is associated with poor outcomes, including high rates of acute graft-versus-host disease.
Sameh Gaballa, MD, MS, assistant professor of medical oncology at Thomas Jefferson University, and colleagues developed a two-step approach to myeloablative allogeneic HSCT for patients with haploidentical or matched-related donors.
In their approach, they administered the lymphoid and myeloid portions of the graft in two separate steps, which allowed fixed T-cell dosing, using cyclophosphamide for T-cell tolerance.
“Making sure we have just the right amount of T cells makes a difference,” Gaballa said in a press release. “Too few and you might not control the cancer, resulting in a relapse or rejection of the transplant. Too many and you run the risk of severe graft-versus-host disease, which can endanger the patient.”
The researchers compared immune reconstitution and clinical outcomes in patients undergoing two-step haploidentical or matched-related HSCT, using a uniform conditioning, graft T-cell dose and GVHD prophylaxis strategy.
Gaballa and colleagues retrospectively reviewed data from patients undergoing the two-step treatment (haploidentical, n = 50; MR, n = 27) for high-risk hematologic malignancies and aplastic anemia. Both groups underwent myeloablative conditioning.
Immune recovery served as the primary endpoint. Clinical outcomes between groups served as a secondary endpoint.
Median follow-up was 38 months (range, 13-95) in the haploidentical group and 48 months (range, 1-76) in the matched-related group.
Patients in the matched-related group had a higher rate of CD-3 and CD-8 cell recovery 28 days following transplantation (median, 98 vs. 39 cells/uL; P = .029). However, both groups had similar overall immune recovery among other T-cell subsets.
Both groups had similar 3-year OS (haploidentical, 70%; matched-related, 71%) and PFS (haploidentical, 68%; matched-related, 70%) probabilities.
The haploidentical group had a 3-year non-relapse mortality rate of 10%, compared with 4% in the matched-related group. Both groups had a similar 3-year incidence of relapse (haploidentical, 21%; matched-related, 27%).
Patients in the haploidentical group had a significantly greater cumulative incidence of grade 2 to grade 4 acute GVHD at 100 days (40% vs. 8%; P < .001); however, the incidence of grade 3 to grade 4 acute GVHD was not statistically significant (6% vs. 4%).
The cumulative incidence of cytomegalovirus reactivation was higher among patients in the haploidentical group (68% vs. 19%; P < .001).
No deaths from infections or GVHD occurred in either group.
The researchers acknowledged the retrospective study design, small patient cohort and use of a single institution as limitations.
“The results of the current study are certainly encouraging and suggest that outcomes from a half-matched related donor are similar to fully matched donors,” Gaballa said. “It might be time to reassess whether half-matched related transplants can be considered the best alternative donor source for patients lacking a fully matched family member donor. For that, we’ll need more evidence from a randomly controlled prospective trial, rather than studies that look at patient data retrospectively, to help solidify our findings here.” – by Cameron Kelsall
Disclosure: The researchers report no relevant financial disclosures.
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