Screening for predictive biomarkers after related and unrelated grafts with posttransplantation cyclophosphamide in adult patients
2 Laboratory of Autoimmune Diagnostics, Pavlov First St. Petersburg State Medical University, St. Petersburg, Russian Federation
There are a number of biomarkers that predict non-relapse mortality (NRM), graft-versus-host disease (GVHD) and relapse incidence (RI) after conventional GVHD prophylaxis based on calcineurin inhibitors with or without antithymocyte globulin. The biologic mechanisms behind the prophylaxis with posttransplantation cyclophosphamide (PTCy) might be different. Currently there is limited data whether the conventional predictive biomarkers work with this type of prophylaxis.
Patients and methods
We conducted a prospective single-center study between 2015 and 2016 in 79 patients. 34% of patients had acute lymphoblastic leukemia, 66% – acute myeloblastic. 68% of patients were in the first complete remission, 27% – in the 2nd and 5% – in the 3rd. 26 received matched related bone marrow (BM) graft with single-agent PTCy GVHD prophylaxis and 53 received unrelated peripheral blood stem cell graft (PBSC) with PTCy, tacrolimus and MMF prophylaxis. Median age was 35 years (range 18-59). The graft was studies extensively studied by flow cytometry (cytometer FACS Aria II, antibodies by Miltenyi biotec). The following populations were analysed: CD3, CD4, CD8, CD16CD56, NKT, iNKT, Treg, double-positive T-cells, double-negative T-cells, TCRalpha/beta, TCR v11 memory cells. The frozen plasma from day +0 was analysed by ELISA (commercial kits by eBioscience) for VEGF A, from day +7 for soluble TNF receptor, IL-8, IL-6, soluble IL-2 receptor, from day+21-30 (after engraftment sample) for ST2, IL-17, soluble TNF receptor. The above mentioned biomarkers were tested in logisted regression for predictive value regarding GVHD and overall survival (OS).
With median follow-up of 15 months overall survival in the study group was 79%, NRM 6%, RI 20%, event-free-survival 75%, acute GVHD grade II-IV 13%, grade III-IV 5%, moderate and severe chronic GVHD 22%. NRM in patients with GVHD was 0%. Despite some predictive value in ROC analysis for acute GVHD of Treg (AUC 0.608), % of CD4 (0.628) and iNKT (0.630), the difference in the GVHD rate was not significant due to small number of events (p>0.07). The predictive biomarker of chronic GVHD was IL-17 measured on day +30 (AUC 0.615), with increased incidence of 57% vs 29%, p=0.017 in patients with elevated level. The most predictive populations for OS were CD3 (AUC 0.626), CD4 (AUC 0.628), CD8 (AUC 0.653), NKT (AUC 0.615), TCRalpha/beta (0.634), iNKT (0.615), iNKT CD8+ (0.613), double-positive T-cells (AUC 0.657). Measured cytokines had lower predictive value for OS than graft composition, except IL-2 receptor (AUC 0.610). The differences in OS was predominantly due to RI. For example, presence of CD8 cells >18% significantly increased the risk of relapse (53% vs 12%, p<0.001). The same trend was observed for other populations. This phenotype with reduced graft-versus-leukemia was independent of the graft source (p=0.57) and occurrence of acute (p=0.37) and chronic GVHD (p=0.50).
The current biomarkers of acute GVHD has limited predictive value after related and unrelated grafts with PTCy, because of the low incidence of this complication and low GVHD-associated mortality. On the contrary we have observed that patients with high prevalence of effector cell populations in the graft have increased RI after transplantation. The explanation of this phenomenon could be elucidated during further studies that evaluate reconstitution of these populations.
The reported study was funded by RFBR, according to the research project No. 16-34-60142 mol_а_dk.
Hematopoietic stem cell transplantation, graft-versus-host disease, cyclophosphamide prophylaxis, biomarkers, efficiency.