Significance of one human leukocyte antigen mismatch on outcome of nonmyeloablative allogeneic stem cell transplantation from related donors using the Mexican schedule.

Using the Mexican approach to conduct nonablative stem cell transplantation (NST), we have prospectively performed 58 allografts in individuals with various malignant and nonmalignant hematological diseases using sibling donors, either HLA identical (6/6) or compatible, with one mismatch (5/6). When comparing allografts obtained from HLA identical (n=40) or compatible (n=18) siblings, respectively, the overall median survival was found to be 33 vs 8 months (P<0.01), the 52-month survival was 47 vs 38% (P>0.2), the prevalence of acute graft-versus-host disease (GVHD) 57 vs 38%, that of chronic GVHD 25 vs 11% and the relapse rate 45 vs 55%. The two patients who failed to engraft were both 5/6 matches. Probably stemming from the low number of patients, and despite a trend toward worse results in patients allografted from HLA compatible (5/6) siblings, most differences in outcome were not significant. It seems that NST can be offered to individuals with either an HLA identical or a compatible sibling donor.