Survival after mesenchymal stromal cell therapy in steroid-refractory acute graft-versus-host disease: systematic review and meta-analysis

Background Graft-versus-host disease (GVHD) is the major limitation of allogeneic haemopoietic stem-cell transplantation (HSCT), for which no approved treatments are available. Use of mesenchymal stromal cells (MSCs) has become standard practice in some European countries, but controversy exists for their benefit. The aim of this meta-analysis was to analyse available evidence for the benefit of MSC treatments in steroid-resistant acute GVHD. Methods We did a systematic review and meta-analysis to assess response to and survival after MSC treatment in patients with steroid-refractory acute GVHD. We searched MEDLINE, Embase, Ovid, and Cochrane Central databases for published studies, and we used ClinicalTrials.gov and other websites to find unpublished studies and conference abstracts. We included prospective and retrospective studies in which MSCs were administered to patients with steroid-refractory acute GVHD. Data were extracted independently by two investigators based on strict selection criteria. A random-effects model was used to pool outcomes across studies because of anticipated heterogeneity. Our primary outcome was survival at 6 months from the first infusion of MSCs. Findings We identified 628 citations with our search, of which 610 were excluded after review and a further five did not contain pertinent data. Thus, our meta-analysis included 13 non-randomised studies at moderate risk of bias, comprising a total of 336 patients. Six studies provided data for the primary outcome analysis (119 patients). Survival at 6 months after MSC treatment was 63% (95% CI 50-74; I-2 = 41%). Survival did not differ with respect to age, MSC culture medium, or dose of MSCs delivered. Interpretation Available evidence suggests that infusion of MSCs could be an acceptable treatment for patients with steroid-refractory acute GVHD. Randomised clinical trials are needed urgently to assess different treatment modalities for steroid-refractory acute GVHD.