Biomarkers in Predicting Response in Patients With Graft-Versus-Host Disease Undergoing Extracorporeal Photophoresis

Inclusion Criteria: * Patients with any NIH subtype of chronic GVHD that is being treated with ECP * Karnofsky Performance Scale (KPS) \> 60% at time of study enrollment * Life expectancy \> 3 months * Steroid dose not greater than 2 mg/kg prednisone equivalent at time of study enrollment * If patient has steroid refractory GVHD (defined as worsening of GVHD after 3 days of 2 mg/kg prednisone equivalent or no improvement after 7 days of 2 mg/kg prednisone equivalent), time interval from start of steroids to initiation of ECP should not be \> 14 days * No use of an investigational agent within 2 weeks of starting ECP * No uncontrolled bacterial, fungal or viral disease (therapy for cytomegalovirus \[CMV\] viremia is permitted) * No evidence of relapse or progression of underlying disease (molecular evidence of relapse/progression or mixed chimerism is permitted) * Women of childbearing potential (WOCBP) should be willing to use 2 forms of contraception; male patients should be willing to use contraception * Voluntary written informed consent before performance of any study-related procedure not part of normal medical care, with the understanding that consent may be withdrawn by the subject at any time without prejudice to future medical care Exclusion Criteria: * Female patients who are breastfeeding or pregnant * Patients known to be human immunodeficiency virus (HIV) positive * Bronchiolitis obliterans as the sole indication of ECP * Serious medical or psychiatric illness likely to interfere with participation in this clinical study * Mechanical ventilation, renal replacement therapy, admitted in intensive care until at time of enrollment * Stage 4 gastrointestinal GVHD as per Seattle-Glucksberg criteria