Cord blood transplantation in Japan

Cord blood transplantation (CBT) has increasingly been used in Japan and the annual number of CBT now exceeds 1,200. The cumulative number of CBT reached 12,853 in 2015, accounting for almost 1/3 of total CBT performed worldwide. It is true that smaller body size and lower costs, as compared to western countries, have been advantages for Japanese people in using CB as graft alternative. In addition, several novel findings regarding serious issues following CBT have been obtained, which further enhanced the use of CB. First, several mechanisms of engraftment failure following CBT other than cell dose have been reported, such as the presence of donor-specific anti-HLA antibodies or the development of hemophagocytic syndrome. Second, unique profiles of infectious complications following CBT have been reported, such as higher incidences of early bacterial infections and HHV-6 encephalitis, as compared to those following bone marrow (BM)/peripheral blood (PB) transplants. Third, the incidence of disease relapse was comparable to those following BM/PB transplants. Novel pre-transplant conditioning regimens using intravenous busulfan have been investigated with promising results being obtained to date. A recent analysis of Japanese transplant registry data revealed similar survival following CBT to HLA-matched unrelated BM/PB transplants.