Noninvasive Assessment of Acute Graft-Versus-Host Disease of the Gastrointestinal Tract After Allogeneic Hemopoietic Stem Cell Transplantation Using ¹⁸F-FDG PET

Acute graft-versus-host disease of the gastrointestinal tract (acute GIT-GVHD) often complicates allogeneic hemopoietic stem cell transplantation (AHSCT). ¹⁸F-FDG PET/CT is known to detect active inflammation and may be a useful noninvasive test for acute GIT-GVHD. The objective of this study was to evaluate the diagnostic utility of ¹⁸F-FDG PET/CT to noninvasively assess patients with clinically suspected acute GIT-GVHD. Fifty-one AHSCT patients with clinically suspected acute GIT-GVHD prospectively underwent ¹⁸F-FDG PET/CT scanning followed by upper and lower GIT endoscopy within 7 d. Endoscopic biopsies of 4 upper GIT and 4 colonic segments were obtained for histology to compare with corresponding quantitative segmental ¹⁸F-FDG PET/CT SUV_max Receiver-operating-characteristic curve (ROC) analysis was performed to determine predictive capacity of ¹⁸F-FDG PET/CT SUV_max for acute GIT-GVHD. A separate qualitative visual ¹⁸F-FDG PET/CT analysis was also performed for comparison. Results: Twenty-three of 51 (45.1%) patients had biopsy-confirmed acute GIT-GVHD, with 19 of 23 (82.6%) having upper GIT and 22 of 22 (100%) colonic involvement. One of 23 patients did not undergo a colonoscopy. GVHD involved the entire colon contiguously in 21 of 22 patients. For quantitative analysis, histology from 4 upper GIT and 4 colonic segments were compared with ¹⁸F-FDG PET/CT SUV_max Colonic segments positive for GVHD had a higher SUV_max (4.1 [95% CI, 3.6-4.5]) than did normal colonic segments (2.3 [1.9-2.7], P = 0.006). No difference was demonstrated in upper GIT segments. Quantitative ¹⁸F-FDG PET/CT yielded a 69% sensitivity, 57% specificity, 73% negative predictive value, and 59% positive predictive value for the detection of GVHD compared with 70%, 76%, 76%, and 68%, respectively, for qualitative analysis. Conclusion: ¹⁸F-FDG PET is a useful noninvasive diagnostic test for acute GIT-GVHD, which when present always involves the colon and usually in its entirety, suggesting colonic biopsy obtained by sigmoidoscopy is adequate for histologic 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.