Prognostic assessment and monitoring of therapy response of intestinal GVHD with sequential FDG-PET scansin a patient with late onset acute intestinal GVHD. (A) The initial scan showed a distinct inflammation of the whole colon. At that time, histopathology of mucosal specimens obtained from different colon segments revealed typical features of GVHD. (B) After 7 days of corticosteroid treatment, re-evaluation by FDG-PET showed nearly normal glucose uptake of the colon in line with almost complete clinical response of the GVHD. (C) After 45 days, clinical relapse of intestinal GVHD was associated with reappearance of increased glucose uptake of the initially affected sites of the colon. These individual results are representative of 4 different patients with repeated FDG-PET examinations after treatment of gastrointestinal GVHD. (D) Comparison of maximum initial FDG uptake in segmental analysis of the bowel showed that patients with fast response to immunosuppressive treatment within 1 week (5 patients) had higher maximal FDG uptake than those 9 patients with slowly responding (4 patients) or refractory (5 patients) GVHD (presentation of median, minimum, and maximum SUV with quartiles of each group). ATG indicates antithymocyte globulin.