18F-FDG-PET for the assessment of acute intestinal GvHD and prediction of response to immunosuppressive therapy.

Abstract Backround : Graft-versus-Host disease (GvHD) is a common complication that increases morbidity and mortality after allogeneic stem cell transplantation (allo-SCT). 18F-FDG-PET imaging has demonstrated to be highly informative for evaluating and mapping of intestinal GvHD. Objective : To corroborate and extend existing findings and to investigate if glucose metabolism assessed by 18F-FDG-PET might be an effective diagnostic tool to predict corticosteroid-refractory acute GvHD and overall survival. Study Design : In this retrospective analysis, 101 patients with clinically suspected acute intestinal GvHD underwent 18F-FDG-PET between 6/2011 and 2/2019. 74 of these patients with clinically and/or histologically proven acute intestinal GVHD as well as positive 18F-FDG-PET findings were analyzed in detail, to assess the predictive value of 18F-FDG-PET regarding response to immunosuppressive therapy and survival. Quantitative PET parameters, particularly the maximum standard uptake value (SUVmax), of patients with fast (clinical improvement and decreased GvHD activity by at least 1 stage after one week of GvHD treatment) or slow/no responses (persisting disease activity for more than 1 week or increasing GvHD activity following first line immunosuppressive therapy) were evaluated. Results : 18F-FDG-PET detected intestinal GvHD with a sensitivity and specificity of 93% (95% CI, 85-97%) and 73% (95% CI, 45-91%), respectively. Patients with fast response to immunosuppressive therapy had a mean SUVmax of 13.7 (95% CI: 11.0- 16.5) compared with a mean SUVmax of 7.6 (95% CI, 7.0-8.3; p .005) observed in patients with prolonged or no response. Median OS of was 573.0 days (95% CI: 539.5–606.5) for patients with fast response versus 255 days (95% CI: 161.0–349.0; P=.009) for patients with slow or no responses. A SUVmax threshold \u003e 8.95 applied to 18F-FDG-PET performed within 100 days after transplantation identified patients with a median OS of 390 versus 117 days for patients with SUVmax ≤ 8.95 (p .036). SUVmax threshold and donor type were independent factors for OS. Conclusions : Our results indicate that 18F-FDG-PET is highly accurate in identifying patients with acute intestinal GvHD and may predict responses to immunosuppressive therapy as well as survival, particularly when applied within the first 100 days after transplant. These results provide a strong rationale to integrate PET-imaging in future prospective trials evaluating new therapies for acute GvHD.