Introduction:The increasing number of unrelated umbilical cord blood (UCB) has been used as an alternative graft because greater degrees of donor-recipient HLA mismatch are tolerated. Generally, lower resolution
HLA typing (antigen-level) for HLA-A and -B and at the allele level for HLA-DRB1 is used to select UCB units; HLA-C and -DQB1 are not typically considered. A few studies have suggested that HLA-matching based upon allelic typing for 8 HLA loci(HLA-A, -B, -C and -DRB1 )should be taken into account when searching UCB units; and the NMDP also encourages extended high-resolution typing of umbilical cord blood units to facilitate further study of the impact of HLA. Nevertheless, few studies have taken into consideration that if HLA-matching based upon allelic typing for 10 loci (HLA-A, -B, -C,-DRB1 and -DQB1) can benefit more patients than traditional HLA typing method (antigen-level for HLA-A,-B and allele-level for HLA-DRB1). In this study, we aim to compare the clinical outcomes between patients using allele-level HLA typing and those using traditional HLA typing method, such as engraftment, relapse and survival after unrelated cord blood transplantation (UCBT).
Patients and methods: 309 patients with hematologic malignancies who underwent UCBT in Anhui Provincial Hospital from May 2008 to December 2015 were analyzed. All patients received a single UCB unit after intensified myeloablative conditioning regimens and a combination of cyclosporine A (CsA) and mycophenolate mofetil (MMF) was given for graft-versus-host disease (GVHD) prophylaxis. Of 309 patients at enrollment, 95 patients used traditional HLA typing method (antigen level for HLA-A,-B and allele level for HLA-DRB1, at least 4/6 HLA loci matching must be met) and 214 patients used allele-level HLA typing method (allele-level for HLA-A,-B,-C,-DRB1 and -DQB1, at least 5/10 HLA loci matching must be met). The follow-up assessment was conducted before May, 31, 2016.
Results: Patients using allele-level HLA typing method had a statistically significant higher cumulative incidence of platelet engraftment (P=0.039), and the risk of grades 2-4 acute GVHD was statistically significant lower than patients using traditional HLA typing method (P=0.01). The risk of transplant-related mortality (TRM) by 1 year was also lower than patients using traditional HLA typing method (P=0.043), while there was no increase in the risk of relapse (P=0.338). Conclusion: Using allele-level HLA typing method when searching UCB units (at least 5/10 HLA loci matching must be met) can improve the engraftment of platelet, reduce the risk of grades 2-4 acute GVHD and TRM, which can take the place of traditional HLA typing method to search UCB units.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.