Chronic graft-versus-host disease in the era of reduced-intensity conditioning

In the past decade the field of hematopoietic stem cell transplantation has entered a new era with the introduction of reduced intensity conditioning (RIC) regimens. The impact of RIC on the incidence of chronic graft-versus-host disease (GVHD) has not been evaluated systematically. Factors confounding such analyses include short follow-up in studies, absence of prospective comparison trials, use of a variety of RIC regimens, lack of uniform GVHD prophylaxis and lack of rigorous criteria for the diagnosis and staging of chronic GVHD. This review discusses factors that appear to influence the incidence and clinical presentation of chronic GVHD in the RIC transplantation era. Overall, RIC seems to decrease the incidence and severity of acute GVHD through day 100 post-transplant when compared to conventional conditioning; however, there is little evidence to suggest that chronic GVHD is reduced after RIC. For the more definitive assessments of chronic GVHD after RIC it will be important to study this question in prospective comparison trials with long duration of follow-up. The recent National Institutes of Health chronic GVHD consensus project recommendations provide now the critically needed standardized guidelines for the diagnosis, classification and staging of chronic GVHD.