Bone-to-Bone Stem Cell Infusion In Graft Failure After Haploidentical Hematopoietic Stem Cell Transplantation: Safety and Feasibility. Three Case Report
Authors: Giglio Fabio , Malato Simona , Clerici Daniela , Messina Carlo , Mastaglio Sara , Claudiani Simone , Gentner Bernhard , Zambelli Matilde , Assanelli Andrea , Matozzo Vincenzo , Corti Consuelo , Bernardi Massimo , Peccatori Jacopo , Ciceri Fabio 
Published: October 2019

Abstract
Abstract 4438

BACKGROUND:
Graft Failure (GF) occurs in 5–27% of patients (pts) after allogeneic hamatopoietic stem cell transplant (HSCT) and is associated with high morbidity and mortality related to infections and hemorrhagic events. Graft function may be poor as result of graft rejection, primary disease relapse or Poor Graft Function (PGF). The incomplete recovery of blood counts is defined primary PGF and the decreasing blood counts after successful engraftment secondary PGF. Several factors may determine GF: disease risk and status, conditioning regimen, HSC source, HLA compatibility, T cell content, immunosuppression, GvHD, viral infections, drugs. GCSF and Rhu-EPO are readily available and effective in PGF but with no effects on platelets. Second transplantation from the same donor, with or without conditioning therapy, can boost the haematopoietic recovery in pts with GF. Unfortunately, both a second peripheral CD34+ mononuclear cells (MNC) mobilization and a marrow harvest in the operating room may be contraindicated early after the first donation as not safe for donors. Intrabone SCT can overcome the risk of graft failure even with a low number of CD34+ MNC, as it has been demonstrated in cord blood transplant. Here we investigate in three adult pts with GF a bone-to-bone boost (BBB) with a small marrow harvest from respective donors, unfit for a second conventional donation.

AIM:
to evaluate the feasibility of the BBB technique in 3 pts with graft failure.

METHODS:
pts were 2 males (57, 53 y) with PGF with a diagnosis of AML and CMML, respectively, and a female (44 y) with graft rejection and AML relapse. In the first two patients prolonged pancytopenia and hypoplastic marrow were documented, with diagnosis of primary PGF and secondary PGF, respectively, donor chimerism ranging from 80–100% (STR and HLA), without evidence of leukemia. In the third patient, after prolonged pancytopenia an AML relapse was documented with 89% blasts on bone marrow aspirate. In PGF patients no conditioning regimen was administered before the boost at day 30 and 72 after SCT, respectively. In the patient with AML relapse Melphalan 200 mg/mq was given 48 h before the infusion, at day 35 after SCT. The 3 donors were related, haploidentical. For the BBB procedure small quantities of bone marrow (< 200ml) were collected from the posterior iliac crest bilaterally of the donors, at the bedside, during deep sedation and analgesya. Shortly after the unmanipulated marrow harvested was infused in superior-posterior iliac crest mono- or bilaterally, depending on the volume, during deep sedation and analgesya. In pt 1 Mononucleated cell (MNC) dose was 0.9 × 10^8/Kg for a volume of 166 ml. In pt 2 MNC dose was 0.4 × 10^8/Kg for a volume of 88 ml. In pt 3 MNC dose was 0.3 × 10^8/Kg for a volume of 140 ml.

RESULTS AND CONCLUSION:
In this cases the BBB technique proved feasible and safe for both the donor and the patient. Patient 1 received a second PBSC boost, without conditioning, 3 months after the BBB, and he's now alive, in CR, 13 months after the first transplant. Patient 2 died 3 months after the first transplant for pneumonia and sepsis. Patient 3 is alive, in CR, 4 months after the first HSCT. This practice can give the chance of HSC boost to patients with GF without the need of a GCSF mobilization for donors, with a minimal invasive operation. This can give the option to overcome and resolve infectious and hemorrhagic complications, bridging patients to further therapies and procedures. The intra-bone SCT may be a facilitating tool for microenvironment reconstitution, seeding and subsequent differentiation and may as well have a tolerogenic effect, through the mesenchymal stromal cells infused with the harvest. Further studies are necessary to assess the efficacy of this procedure.

Disclosures:
No relevant conflicts of interest to declare.