LOW Tranplant Related Mortality and LOW GRAFT Rejection After Related Haploidentical STEM CELL Transplantation (HAPLO-SCT) Prepared with NON Myeloablative CONDITIONING REGIMEN (NMA) and Posttransplant Cyclophosphamide for Advanced Lymphoid Malignancies.
Authors: Furst Sabine , Crocchiolo Roberto , El-Cheikh Jean , Faucher Catherine , Oudin Claire , Granata Angela , Venton Geoffroy , Lemarie Claude , Coso Diane , Bouabdallah Reda , Stoppa Anne Marie , Vey Norbert , Chabannon Christian , Blaise Didier 
Published: October 2019

Abstract
Abstract 3031

Introduction:
The use of hematopoietic stem cells from partially matched family donors has become an alternative transplant option for patients with no HLA identical donor available. It might be even a first choice, especially in advanced hematological maligancies, because of the presumed stronger graft versus tumor effect relied to the partial HLA identity. However, haplo-SCT is associated with high risk of graft rejection (GR) and severe graft versus host disease (GvHD), especially after non NMA. High dose posttransplant Cyclophosphamide (Cy) has been shown to prevent GvHD and GR.

Aim:
This retrospective analysis report the outcome of 15 patients (pt) using posttransplant Cy after a NMA in our center.

Results:
Fifteen adult pt (Male=9) with high risk lymphoid malignancies for whom a HLA matched related or unrelated donor were not available, underwent haplo-SCT from February 2011 to June 2012. The median pt age was 41years (y) (range, 20–60). Diagnosis were Hodgkin Lymphoma in 5 pt, Non Hodgkin Lymphoma in 4 pt, Chronic Lymphatic Leukemia in 2 pt, Multiple Myeloma in 2 pt and Acute Lymphoblastic Leukemia in 3 pt. All pt were heavily pretreated with a median of 3 or more chemotherapy regimens including failure of previous autologous (12pt) or allogeneic transplantation (3pt). At time of transplant 9pt (60%) were in complete remission (CR1=6, CR2=3). The NMA consisted in Fludarabine 30mg/m2 iv on days -6 to -2, Cyclophospamide 14.5mg/kg iv from days -6 and -5 and Total Body Irradiation 200cGy on day -1. For Graft versus Host Disease prophylaxis all pt received postransplant Cy 50mg/kg iv on days + 3 and +4 with Mesna. One day later, all pt started with Cyclosporine (CSA) 3mg/kg/day and Mycophenolatemofetil (MMF) 15mg/kg/day and Filgrastim 5ug/kg/day until neutrophil recovery. MMF was stopped at day+35 and CSA was given until day +180 in the absence of GvHD. Ten pt (67%) received bone marrow (BM) and 5 pt (33%) G-CSF mobilized peripheral blood stem cells (PBSC) as graft source. All donors were HLA haploidentical first degree family donors (Male=8) including brothers (7), sisters (2), mothers (4) and son (1). Median donor age was 49 y (range, 23–66). Pt had HLA typing at the allele or antigen level (A, B, Cw, DRB1, DQ) whereas 8 pt were mismatched at 5 loci, 1 pt at 4 loci, 4 pt at 3 and 2 pt at 2 loci. BM grafts contained a medium of 2×106/kg CD34+ cells and 22×106/kg CD3+ cells. PBSC grafts contained a medium of 6×106/kg CD34+ cells and 298×106/kg CD3+ cells. The engraftment rate was 93%, with a median time to neutrophil recovery (>500 G/l) of 20.5 days (range, 14–26) and to platelet recovery (>20 000 G/l) of 28.5 days (range, 14–41). Compared to BM recipients, pt receiving PBSC experienced faster neutrophil [(17 days (range, 14–23) vs 21 days (range, 18–26), p=0.04] and platelet recovery [(23 days (range, 14–30) vs 30 days (range, 23–41), p=0.04)]. One pt with ALL did not engraft and died at day +40 for infectious complication. One pt died of treatment related mortality with a cumulative incidence of 7% [96%CI (0–20)]. Two pt developped acute GvHD grade 2. No chronic GvHD was observed in pt surviving beyond day 100. Four pt exerienced relapse or progression of the underlying disease. After a median follow up of 197 days (range, 40–518) the actuarial overall survival and event-free survival at 2 years were 87% [95% CI (70–100)] and 51 % [95% CI (16–85)], respectively.

Conclusion:
NMA haplo-SCT with postransplant Cy in pt with advanced lymphoid malignancies is associated with low NRM, low acute GvHD and low graft rejection. However, better disease control in selected pt is needed to overcome early relapse or progression. Even if follow-up is short, PBSC seems to be an promising option to bone marrow as stem cell source.

Disclosures:
No relevant conflicts of interest to declare.