Evaluation of the Relationship Between Increased HLA Incompatibility Rate and Relapse/Survival in Haploidentical Stem Cell Transplantation

HLA mismatch and outcomes in haploidentical HSCT

Abstract

Objective Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment option for patients with high-risk hematologic malignancies; however, complications related to HLA mismatch remain a major concern. This study aimed to retrospectively evaluate the relationship between the degree of HLA mismatch and relapse or survival outcomes in patients undergoing haploidentical HSCT.

Materials and Methods 95 patients who underwent haploidentical HSCT between 2013 and 2021 at Florence Nightingale Hospital were retrospectively analyzed. All patients had a minimum follow-up of 12 months. Patients were classified according to the degree of HLA compatibility (4/10–8/10 matched, with antigen or allele mismatch). Associations between patient, donor, and transplant characteristics and outcomes including disease-free survival (DFS), overall survival (OS), relapse, graft failure, and graft-versus-host disease (GVHD) were assessed using the Kaplan–Meier method.

Results Diagnoses included AML(37.9%), ALL(31.6%), CLL(2.1%), MDS(5.3%), NHL(17.9%), and HL (5.3%). Complete remission was achieved in 74.7% of cases. Myeloablative conditioning was administered in 87.4% of patients. Post-transplant cyclophosphamide was the most frequently used GVHD prophylaxis. Acute and chronic GVHD developed in 36.8% and 33.7% of patients, respectively. Relapse occurred in 21.1% of cases. No statistically significant relationship was found between HLA mismatch degree and OS, DFS, relapse, or GVHD incidence.

Conclusion The degree of HLA mismatch showed no significant impact on survival or transplant-related outcomes when evaluated alongside disease, patient, donor, and transplant-related factors. These results support haploidentical HSCT as a safe and feasible alternative for patients lacking a fully HLA-matched donor.