Prospective observational study on the first 51 cases of peripheral blood stem cell transplantation from unrelated donors in Japan.

The Japan Marrow Donor Program (JMDP) has facilitated unrelated peripheral blood stem cell transplantation (URPBSCT) since 2010. We conducted a prospective multicenter observational study to evaluate the feasibility of such transplantation. Between 2011 and 2014, 51 patients underwent URPBSCT from 8/8 allele-matched donors for hematological malignancies. The median age of the patients was 50 years; 21 had high-risk disease. Myeloablative conditioning regimens were used in 31 patients, and tacrolimus based graft-versus-host disease (GVHD) prophylaxis was used for all patients. The cumulative rate of engraftment was 96%. With a median follow-up period of 610 days for survivors, 100-day and 1-year overall survival rates were 86 and 59%, respectively. The cumulative incidence of non-relapse mortality and relapse at 1 year were 14 and 35%, respectively. The incidence of grade II to IV acute GVHD at 100 days and extensive type of chronic GVHD at 1 year were 25 and 32%, respectively. The probability of overall survival was comparable with that of bone marrow transplantation from HLA matched-unrelated donors in Japan, although the incidence of chronic GVHD was higher. Further follow-up with more patients is clearly warranted to establish the optimal use of URPBSCT together with the approaches of minimizing chronic GVHD.