Unrelated-donor marrow transplants: the experience of the National Marrow Donor Program.

As of December 1994, more than 3,000 marrow transplants had been accomplished using unrelated donors provided by the National Marrow Donor Program. With more than 1.5 million donors listed in the registry, over 60% of patients now find an HLA-A,B,DR phenotypic match at the initial search. The HLA types of these patients are biased toward the common Caucasian haplotypes, but the likelihood of identifying donors for non-Caucasian patients has improved with time. Analysis of the first 462 transplants showed disease-free survival (DFS) at 2 years to be approximately 40% in good-risk patients and 20% in poor-risk patients. Chronic myelogenous leukemia transplanted within the first year after diagnosis had 45% DFS. Some recent reports from individual transplant centers demonstrate results closer to those obtained with sibling donors, while a limited retrospective comparison suggests that unrelated-donor transplants are at least equivalent to and probably better than autologous transplants. A single HLA mismatch at A, B, or DR can be tolerated, but results are better with phenotypic identity. The most recent NMDP analysis has also identified younger donors and male donors as favorable variables in evaluating one-year survival of unrelated-marrow recipients.