High plasma IL-6 levels following haploidentical allogeneic hematopoietic stem cell transplantation post-transplant cyclophosphamide as predictor of early death and worse outcome

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) can be used as an alternative procedure in the absence of HLA-compatible donors. The use of high doses of cyclophosphamide after infusion improves the prognosis and eliminates the need for T cell depletion in vivo. Among the main complications of haplo-HSCT are acute graft-versus-host disease (a-GVHD) and cytokine release syndrome (CRS). This is a systemic inflammatory response that leads to the release of inflammatory proteins, including IL-6. This syndrome has several clinical features, with mild to severe symptoms. This study aimed to compare plasma IL-6 levels in patients submitted to different HSCT types and to associate them with the presence of acute graft versus host disease (a-GVHD), CRS and survival. A total of 84 patients (22 haploidentical and 62 non-haploidentical) were evaluated at different times. The IL-6 levels in haplo and non-haplo-HSCT recipients were measured before transplantation and on days D7, D14, D28, D60, and D100. IL-6 levels were higher in haplo-HSCT recipients than in non-haplo-HSCT recipients, remaining elevated from D14 until D100 (P = 0.006) and a cut-off ≥11 pg/mL on D7, which is related to worse overall survival. In our study, we found no association with a-GVHD (P = 0.239), a common complication of this type of transplant, but we found a relationship between the increase in IL-6 and CRS (P = 0.021). IL6 can be used as a biomarker for patients submitted to haplo-HSCT, allowing clinical interference in patients having levels of IL-6 times larger than normality values, avoiding early death in this group of patients. •Haploidentical hematopoietic stem cell transplantation can be used as an alternative procedure in the absence of HLA-compatible donors.•Acute graft-versus-host disease and cytokine release syndrome are among the main complications of haplo-HSCT.•Cytokine release syndrome is a systemic inflammatory response that leads to the release of inflammatory proteins, including IL-6.•A cut-off of ≥11 pg/mL on D7 in PT/Cy-haplo recipients is related to worse overall survival.•Plasma IL-6 measurement may be a good biomarker, allowing a therapeutic approach in this group of patients, thus avoiding the worst outcome of the transplant.