Abstract

Both total nucleated cell (TNC) dose and human leukocyte antigen (HLA)-match affect the outcome of cord blood (CB) transplantation. However, how to prioritize these characteristics in unit selection is not established. Therefore, we analyzed the outcomes of 1061 patients who received single-unit myeloablative CB transplantation for leukemia or myelodysplasia. TNC dose and HLA-match each affected survival via their effect on transplant-related mortality (TRM); neither was associated with relapse. Therefore, TRM was the focus of multivariate analyses combining dose and HLA-match. Compared with our 1 HLA-mismatch (MM) reference group with TNC 2.5 to 4.9 x 10(7)/kg, recipients of 0 MM units had the lowest TRM regardless of dose (relative risk [RR] = 0.4, P = .019). TRM for recipients of 1- or 2-MM units with TNC 5.0 x 10(7)/kg or greater was similar to the reference group (RR = 0.8, P = .391 and RR = 1.0, P = .847) despite their greater dose. Recipients of 2 MM units with TNC 2.5 to 4.9 x 10(7)/kg had a greater TRM (RR = 1.5, P = .014), and those with 1 or 2 MM and TNC less than 2.5 x 10(7)/kg or 3 MM did substantially worse. These findings support new unit selection criteria that take into account both TNC dose and HLA-match and have important implications for the size of the global CB inventory needed to find an optimum CB graft.