The impact of donor‐specific anti‐HLA antibody levels on primary poor graft function and graft rejection in rituximab desensitized haploidentical stem cell transplantation

This study investigates the influence of donor‐specific anti‐HLA antibodies (DSA) levels on primary poor graft function (PGF) and graft rejection (GR) after haploidentical stem cell transplantation (haplo‐SCT) with rituximab desensitization. A total of 155 DSA‐positive haplo‐SCT candidates with mean fluorescence intensity (MFI) between 2000 and 10,000 were enrolled in this prospective clinical trial. Receiver operating characteristic (ROC) curves determined the optimal DSA MFI cutoff for identifying high‐risk patients. Patients were categorized into two groups: DSA low‐level group (2000 ≤ DSA MFI < 5000, Group A) and high‐level group (5000 ≤ DSA MFI ≤ 10,000, Group B). The incidence of primary PGF was 6.5% (2.6%–10.3%), while GR incidence was 0.6% (0.0%–1.9%). Group A had significantly lower primary PGF rates than Group B (2.3% [0.0%–5.7%] vs. 12.9% [4.8%–21.0%], p = 0.017). Only one patient in Group B experienced GR. High DSA levels (5000 ≤ MFI ≤ 10,000) were identified as the sole independent risk factor for primary PGF and GR after haplo‐SCT with rituximab desensitization (HR = 7.282, 95% CI 1.517–34.953, p = 0.013). The 4‐year cumulative incidence of relapse, non‐relapse mortality, disease‐free survival, and overall survival were 14.7% (11.6%–17.8%), 16.3% (13.1%–19.4%), 69.0% (65.9%–76.2%), and 70.6% (66.4%–74.8%), respectively. DSA levels have an impact on efficiency of rituximab desensitization, and a DSA MFI threshold is provided for predicting primary PGF and GR.