Steroid-Refractory Acute Gvhd in Children: Retrospective Analysis of the AIEOP HSCT Registry
Authors: Zecca Marco , Pagliara Daria , Fagioli Franca , Rovelli Attilio , Lanino Edoardo , Prete Arcangelo , Calore Elisabetta , Boghen Stella , Merli Pietro , Compagno Francesca , Ripaldi Mimmo , Porta Fulvio , Locatelli Franco 
Published: October 2019

Abstract
Introduction. Severe acute graft-versus-host disease (GVHD) remains the most relevant complication after allogeneic HSCT. Although its incidence in the pediatric population is lower than in adults, children with severe acute GVHD and who do not respond to first-line treatment with systemic steroids still have a poor prognosis. The exact incidence of steroid-refractory acute GVHD in children is still not precisely defined, as well as the risk of non-relapse mortality (NRM) due to steroid-refractory acute GVHD. Aim of our study was to analyze the frequency of acute GVHD unresponsive to first-line steroid treatment in children and adolescents given allogenic HSCT, to describe the second line treatment employed, and the outcome of patient with this complication.
Patients and methods. This retrospective study included patients younger than 18 years at the time of transplantation and given a first allogeneic HSCT between 2010 and 2015 in one of the HSCT Centers of the Italian Association for Pediatric Hematology / Oncology (AIEOP). Overall, 1608 patients (59% M and 41% F) were analyzed. Median age at HSCT was 8 years (range 0.2 - 18) 1084 (67%) were affected by malignant diseases and 524 (33%) by non-malignant disorders. The donor was an HLA-matched family donor (MFD) in 28% of cases, an unrelated donor (UD) in 52% and an HLA-haploidentical family donor in 20%. In MFD transplants Cyclosporine (CSA) was used as GVHD prophylaxis in 30% of cases and the combination of CSA + short-term methotrexate (MTX) in 48%. 75% of UD transplant recipients received CSA + MTX + anti-thymocyte globulin (ATG) as GVHD prophylaxis, and 25% other drug combinations. Ex vivo T-cell depletion of the graft was employed in most patients given a HLA-haploidentical HSCT (79% of transplants), and high-dose post-transplant cyclophosphamide in 11% of cases.
Results. The cumulative incidence (CI) of grade II-IV acute GVHD was 31%, while that of grade III-IV acute GVHD was 10%. The overall incidence of chronic GVHD was 13% and that of extensive chronic GVHD was 6%. The CI of NRM was 14% for grade 0 acute GVHD patients, 9% for grade I, 11% for grade II, 26% for grade III and 68% for grade IV (P < 0.001). Of the 491 patients with grade II-IV acute GVHD, 250 (51%) required a second-line treatment after first-line steroid therapy (30% of grade II, of 75% grade III and 83% of grade IV patients). Acute GVHD requiring second-line treatment was more frequent in UD transplant recipients (21% of patients) than in matched sibling or haploidentical donor recipients (7% and 13% respectively, P < 0.01), while age at HSCT and diagnosis (malignant vs. non-malignant disease) were not associated with this complication. Second-line treatment was extracorporeal photochemotherapy in 60% of patients, mofetil mycophenolate (MMF) in 46%, mesenchymal stromal cells (MSC) in 12%, monoclonal antibodies (MoAbs) in 5% and other treatments in 28%; 32% of patients received more than one second line treatment. Overall NRM was 13% for patients with grade 0-I acute GVHD, 15% for grade II-IV responding to steroids, and 25% for grade II-IV patients requiring second-line therapy (P < 0.001). The addition of a second-line treatment partially decreased NRM only in patients with grade IV acute GVHD, but the difference was not statistically significant (66% vs. 78%; P = 0.313). In multivariable analysis, grade III (HR = 1.84; P = 0.044) and grade IV acute GVHD (HR = 7.07; P < 0.001), and the use of an UD (HR = 1.63; P = 0.007) were associated with an increased NRM, while the use of a second-line treatment did not decrease this risk (HR = 0.80; P = 0.368).
Conclusions. Despite being less frequent than in adults, severe steroid-refractory acute GVHD is still associated with a very high NRM also in pediatric patients. Second or third-line treatments adopted so far have not been effective in improving control of the complication and in decreasing NRM. The prospective evaluation of acute GVHD biomarkers (such as ST2 and REG3α) could help in identifying patients at higher risk of NRM. Prospective studies are warranted to define new treatment modalities that could decrease the mortality rate associated with the most severe form of disease.

Disclosures
Zecca: Chimerix: Honoraria. Locatelli:bluebird bio: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees; Miltenyi: Honoraria.