«Graft-Versus-Host» Disease after Haploidentical Hematopoietic Stem Cell Transplantation from Relative Donors in Children with Cancer, Prophylaxis Regimens and Correlation with «Graft-Versus-Tumor» Effect: a Retrospective Cohort Study

Background. «Graft-versus-host» disease (GVHD) is a major complication of allogeneic Hematopoietic Stem Cell Transplantation (HSCT), the main cause of non-relapse mortality. The actual problems of alternative donors HSCTs are GVHD prophylaxis and its distinction from «graft-versus-tumor» (GVT) effect. Objective. Assessment of incidence and severity of GVHD in children with very high-risk cancer after non-T-depleted haplo-HSCT; searching some correlation between controlled chronic GVHD (chGVHD) and GVT effect after HSCT, compare cyclosporine (CSA) and tacrolimus based GVHD prophylaxis. Methods. We provided the GVHD assessment in 74 recipients of haplo-HSCs from relatives since 2001 till 2018 in retrospective cohort study. Effect of chGVHD on the HSCT results was assessed in 23 patients with acute myeloid leukemia (AML) and 15 patients with solid tumors. We analyzed the incidence of severe acute and chronic GVHD in patients who received CSA or tacrolimus-based prophylaxis. Results. The incidence of severe aGHVD in our study was 15%, chGVHD — 12%. Switch CSA to tacrolimus resulted in reduction of severe aGVHD from 21% to 9% and full elimination of severe extensive chGVHD. Controlled chGVHD after haplo-HSCT was associated with relapse reduction from 48.7% to 30% and improvement of overall survival (OS) from 46.5% to 80.8% in patients with AML. We haven’t seen any clinically significant antitumor effect of graft in patients with solid tumors. Conclusion. In our study the incidence of severe GVHD corresponds to world data after HSCTs from alternative donors, it went down after switch from CSA to tacrolimus. We found some correlation between controlled chGVHD development and HSCT results improvement in patients with AML. The GVT effect of haplo-graft in solid tumors is almost absent.