Unit selection for umbilical cord blood transplantation for adults with acute myeloid leukemia in complete remission: a Japanese experience.

To investigate optimal unit selection for umbilical cord blood transplantation (UCBT), we conducted a registry-based study of 1355 adults with acute myeloid leukemia in first or second complete remission who underwent single-unit UCBT. To be eligible for analysis, UCB units had to contain a total nucleated cell (TNC) dose of 2.0 × 107/kg or higher and present at least a 4/6-match for HLA-A, -B, and -DR antigens in line with clinical practice in Japan, both of which are less stringent criteria than those used in Western countries. Neither TNC dose nor the degree of HLA matching affected survival (P = 0.138 and P = 0.696, respectively). As for HLA-A, -B antigens and -DRB1 allele, better HLA matching was associated with lower non-relapse mortality (P = 0.011) but higher relapse (P = 0.046), resulting in no improvement in survival (P = 0.680). Taking the allele level for each HLA-A, -B, and -DRB1 into consideration was less useful for predicting non-relapse mortality (P = 0.198). These findings suggest that the less stringent criteria for UCB unit selection are acceptable for Japanese patient population and perhaps even more beneficial in terms of providing a better chance to find a suitable UCB unit.