FDG-PET/CT for the detection of gastrointestinal graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT)

Objectives Acute GVHD of the gut (usually occuring within 100 days post-allo-HSCT) is a major complication after allo-HSCT. The current reference standards for diagnosis combine both clinical symptoms and histopathology findings. However, this diagnosis approach remains unsatisfactory in many cases and more specific diagnosis tools are needed. A recent study suggested that the inflammatory activity associated with gut acute GVHD can be detected by FDG-PET/CT (Blood, 2008, 111:2009-18). The aim of this prospective study was to assess the potential predictive value of FDG-PET/CT for the early diagnosis of acute gut GVHD.

Methods Between January 2009 and March 2010, 43 allo-HSCT patients (of whom 16 had some digestive symptoms) were enrolled in this prospective study and underwent FDG-PET/CT at a median of 29 days after allo-HSCT (range, 24-67). FDG-PET/CT was performed using a Discovery LS hybrid PET scanner (GE), 60 min after injection of 5-7 MBq of FDG and blindly evaluated by 2 experienced nuclear medicine physicians. Any focal or diffused increased FDG uptake exceeding physiologic digestive activity was defined as pathological. In parallel, clinical monitoring for GVHD signs and histopathology (whenever available or appropriate) was performed.

Results During follow-up, 11 patients were diagnosed with acute GVHD according to standard criteria, while 32 patients remained free of GVHD symptoms. FDG-PET/CT was considered as positive in 13 cases (7 true-positive and 6 false-positive results) and negative in 30 cases (26 true-negative and 4 false-negative results). Specificity, sensitivity, positive predictive value, negative predictive value (NPV) and accuracy of FDG-PET/CT were 64%, 81%, 54%, 87% and 77% respectively. Interestingly, among the 27 non-symptomatic patients, NPV reached 96%.

Conclusions These first results suggest a potential benefit of FDG-PET/CT for the early diagnosis of acute gut GVHD, with a hight NPV, allowing to avoid invasive diagnostic procedures