Poor Graft Function in Recipients of T Cell Depleted (TCD) Allogeneic Hematopoietic Stem Cell Transplants (HSCT) Is Mostly Related to Viral Infections and Anti-Viral Therapy.

Abstract Abstract 3147 Introduction: Poor graft function (PGF) without immune rejection, defined as persistent cytopenias with hypocellular marrow and full donor myeloid chimerism, can be a life-threatening complication after allogeneic HSCT. It is commonly caused by viral infectious, myelosuppressive drugs like antivirals, and graft-vs-host disease (GvHD). Treatment options include supportive therapy with transfusions and growth factors and in severe cases administration of additional hematopoietic stem cells (HSCs) from the same donor without conditioning (stem cell boost). The incidence, natural history, and the indications for stem cell boost therapy are not well defined. Aims: To assess the incidence, etiologies, and indications for stem cell boost for PGF in a homogeneous group of patients with advanced MDS and AML who underwent TCD HSCT from matched or mismatched related or unrelated donors after conditioning with the same myeloablative regimen. Patients and methods: Poor graft function was defined as persistent neutropenia (ANC Results: Forty-one patients were evaluable for this analysis; 1 patient was not included as he rejected the allograft shortly after engraftment. There were 8 cases of PGF with a cumulative incidence (CI) at 1 year of 18% (13% HLA matched, 33% HLA mismatch). The etiology was infection in 7 cases, and unknown in the 8th case. This patient presented with presumed autoimmune anemia and thrombocytopenia associated with a hypercellular marrow and did not respond to multiple lines of therapies. Her marrow became later hypocellular and met the criteria for PGF. None of the PGF cases in this series was associated with GvHD at the time of diagnosis of PGF. The infectious etiologies included: 6 viral infections and 1bacterial sepsis + myelosuppressive drugs. The most common viral etiology associated with PGF was CMV (50%). The 1-year CI of PGF in CMV seropositive patients was 25% and in CMV seronegative patients was 14%. Of note, HHV6 viremia was detected in patients with PGF. HHV6 is not routinely monitored, however, making it difficult to establish a causative role. All patients had moderate PGF at diagnosis and 3 cases had worsening of cytopenias and met the criteria for severe PGF. To date, 3 PGF patients have died from EBV-PTLD, adenovirus infection or GVHD (developed after CMV treatment with liposomal cidofovir), 3 continue to suffer from PGF and 2 patients are alive with recovered good blood counts after eradication of CMV. Of the 3 patients with persistent PGF, one received a TCD boost with no response, and 2 continued to be treated for CMV viremia. A stem cell boost was indicated if pancytopenia persisted despite eradication of cause of the PGF. In this small series, there were not enough events to evaluate association between PGF and CD34 cell dose, CD3 cell dose or day 100 T-cell chimerism. Conclusions: In this homogenous population of patients with MDS who underwent TCD allogeneic HSCT, the incidence of PGF is about 20%. The most common cause was viral infection with predominance of CMV. Therefore, strategies to prevent CMV reactivation in patients undergoing allogeneic HSCT has the potential to reduce the risk of PGF and avoid the need for infusion of additional stem cells. Download : Download high-res image (11KB) Download : Download full-size image Disclosures: No relevant conflicts of interest to declare.