P019 The impact of HLA haplotype and allele mismatches of donor-recipient pairs on outcomes of haploidentical stem cell transplantation with a third part cord blood unit

Aim To analyze allele mismatches of HLA-A, -B, -C, -DRB1, -DQB1 and haplotype mismatch of donor-recipient pairs on the outcome of haploidentical transplantation combined with a third part cord blood unit. Methods 230 pairs of donor-recipient were performed HLA-A, B, C, DRB1, DQB1 typing using SBT and SSOP methods from January 2012 to December 2014. Results Pairs were divided into HLA-5/10, 6/10, 7/10 and ⩾8/10 groups according to HLA-A, B, C,DRB1 and DQB1 high resolution typing and matched degrees, the 3-year probability of overall survival (OS) for each group were 48.7%, 59.3%, 71.1%, 38.3%( P  = 0.068) respectively. HLA>6/10 matched group associated with significant favorable effect on OS compared with HLA-5/10 matched one ( P  = 0.041).When the HLA class I antigen matched on the recipient and donor, improved OS and event free survival (EFS) in HLA-6/10 matched group than in HLA-5/10 matched one ( P  = 0.017, P  = 0.088), especially in single HLA-A loci allele matched one ( P  = 0.013, P  = 0.013), were observed. As to the third part cord blood unit, sharing the same haplotype with the recipient-donor pairs produced better platelet recovery than the misfit one (95.3% vs 86.2%, P  = 0.007), similar result was found in terms of neutrophil recovery (98.8% vs 96.1%, P  = 0.022). Conclusions HLA locus mismatch and haplotype mismatch of the donor and recipient should be useful for selection of the most optimum donor. Co-infused of an unrelated cord blood unit sharing the same haplotype with the recipient-donor pairs could improve hematopoietic recovery.