Non-Invasive Assessment of Acute Graft vs. Host Disease of the Gastrointestinal Tract Following Allogeneic Haemopoietic Stem Cell Transplantation Using 18F-FDG PET

Abstract

Background: Acute graft versus host disease of the gastrointestinal tract (Acute GIT-GVHD) often complicates allogeneic haemopoietic stem cell transplantation (AHSCT). 18F-FDG PET/CT (PET) is known to detect active inflammation and may be a useful non-invasive test for Acute GIT-GVHD. Objective: To evaluate the diagnostic utility of PET to non-invasively assess patients with clinically suspected Acute GIT-GVHD. Study Design: 51 AHSCT patients with clinically suspected Acute GIT-GVHD prospectively underwent PET scanning followed by upper and lower GIT endoscopy within 7 days. Endoscopic biopsies of 4 upper GIT and 4 colonic segments were obtained for histology to compare with corresponding quantitative segmental PET SUVmax values. Receiver operator characteristic curve (ROC) analysis was performed to determine predictive capacity of PET SUVmax for Acute GIT-GVHD. A separate qualitative visual PET analysis was also performed for comparison. Results: 23/51 (45.1%) patients had biopsy confirmed Acute GIT-GVHD, with 19/23 (82.6%) having upper GIT and 22/22 (100%) colonic involvement. 1/23 did not have colonoscopy. GVHD involved the entire colon contiguously in 21/22 patients. For quantitative analysis, Histology from 4 upper GIT and 4 colonic segments were compared with PET SUVmax values. Colonic segments positive for GVHD had higher SUVmax, 4.1 [3.6-4.5] compared to normal colonic segments 2.3 [1.9-2.7], P = 0.006. No difference was demonstrated in upper GIT segments. Quantitative PET yielded 69% Sensitivity, 57% Specificity, 73% Negative and 59% Positive predictive value for detection of GVHD compared to 70%, 76%, 76% and 68% respectively for qualitative analysis Conclusion: 18F-FDG PET is a useful non-invasive diagnostic test for Acute GIT-GVHD which when present always involves the colon and usually in its entirety. This suggests colonic biopsy obtained by sigmoidoscopy is adequate for histological confirmation when Acute GIT-GVHD is suspected. Of note, 18F-FDG PET cannot distinguish Acute GIT-GVHD from non-GVHD inflammatory changes in the colon.