ABSTRACT
Hematopoietic stem cell transplantation (SCT) provides effective therapy for patients with
lymphohematopoietic, immunological, metabolic, and other disorders. Current estimates
of annual numbers of allogeneic SCT are 12,000-15,000 worldwide, with continuing
growth rate of 10-20% per year (1). Transplant-related mortality at 1 year after HLA-
identical sibling transplants is about 30% (2). Long-term survivors are at risk for late
complications. In the early 1990s chronic graft-vs.-host disease (GVHD) was the most
common late complication of allogeneic SCT, with reported incidences ranging from
30 to 80% (3). Although prevention and treatment of acute GVHD have improved over
the past two decades, similar progress in chronic GVHD has remained elusive as it con-
tinuous to be the leading cause of late nonrelapse mortality following allogeneic SCT
(4). Beneficial graft-vs.-leukemia/lymphoma (GVL) effect on survival was offset by the increased nonrelapse mortality secondary to infections and organ failure during the course
of chronic GVHD. Not surprisingly, large observational studies identified chronic GVHD
as the most common cause of nonrelapse deaths occurring more than 2 years posttrans-
plant, and increasing severity of chronic GVHD is associated with higher mortality
rates (5,6). In aplastic anemia and refractory anemia where the risk of relapse and death
from the primary disease is low, chronic GVHD has a substantial adverse impact on sur-
vival that has not improved significantly over the past 30 years (7,8). Przepiorka et al.
