For patients who survive allogeneic bone marrow transplants greater than 100 days, chronic GvHD is a major cause of non-relapse morbidity and mortality. Depending on the presence of known associated risk factors, chronic GvHD will occur in 20-50% of these transplant recipients, with mortality rates varying from 20 to 70%.

Because a lymphocyte-mediated immune reaction is thought to be involved in GvHD, suppression of these cells by means other than medications could have benefit in the GvHD population.

ECP is a technique in which peripheral white blood cells are exposed to a photoactivatable compound (UVADEX) administered extracorporeally and ultraviolet A light. After cells are reinfused into the patient, their function is altered, thereby activating mechanisms that allow for further regulation of specific lymphocyte populations.

The purpose of this study is to determine whether ECP, in conjunction with standard therapy, is effective in the treatment of chronic GvHD. Efficacy of the therapy with respect to skin manifestations of the disease will be determined by a blinded skin assessor.