Donor Source

Unrelated transplantation is perceived by many clinicians to be substantially more dangerous than transplantation using sibling donors. Although overall sustained LFS is roughly 10% lower using unrelated donors, according to international registry data, results in selected patients closely resemble those achievable with siblings. Patients aged 50 years or younger, with well-matched donors, who undergo transplantation within a year of diagnosis, have sustained survival rates of approximately 70%.29

The difference in outcome between siblings and matched unrelated donors is closely related to the degree of HLA incompatibility between donor and recipient (Figure 37.4). Patients with chronic phase CML within 2 years of diagnosis, mismatched at a single HLA-A, B, C, DRB1, or DQB1 allele have a significantly worse outcome than their counterparts with no mismatch. A single mismatch of an HLA-C allele or antigen, an occurrence largely unrecognized historically because of the failure to prospectively match donor-recipient pairs at this site, confers a significantly increased risk of mortality.49

Multiple mismatches further increase transplant risk. Those involving HLA-DQB increase mortality compared to those not involving HLA-DQB.49 These findings emphasize the necessity of performance of and appropriate analysis of molecular typing of HLA alleles for donor selection.

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