ALBERT

Description: Abstract 2241 Poster Board II-218 Introduction: T-LGL has the phenotype characteristics of a post-thymus mature T cell. Expansion of T-LGL has been reported to occur in association with viral infections, autoimmune diseases, lymphoproliferative malignancy and HSCT. The clinical significance of finding T-LGL expansion post HSCT is unclear. We recently reviewed the incidence of T-LGL expansion in patients who underwent allogeneic HSCT in our institution. We specifically asked whether T-LGL expansion was associated with increased viral infections, stable chimerism, graft-versus-host disease (GvHD), recurrence of primary disease, and overall survival. Patients and Methods: A retrospective analysis was done on all adult patients who underwent allogeneic HSCT at the Karmanos Cancer Institute between January 1, 2004 to June 30, 2009. In patients with persistent lymphocytosis (〉3000 cells/mm3) post HSCT, expansion of T-LGL phenotype was identified by flow cytometry (CD2, CD3, CD5, CD7, CD8 and CD57 positive) and clonality was confirmed by T cell receptor beta and/or gamma gene rearrangement (TCR-GR) using southern blot analysis and polymerase chain reaction (PCR). Results: A total of 547 patients underwent allogeneic HSCT during the study period. We identified T-LGL expansion in 24 patients with persistent lymphocytosis using flow cytometry. Median age of patients with T-LGL expansion was 50 years (range 24-68 years). Median time to diagnosis was 275 days post HSCT (range 69-1454 days) and median duration of follow-up was 811 days (range 85-1701 days). All 24 patients achieved full donor chimerism post transplantation by STR analysis. Fourteen out of 24 patients with T-LGL expansion had positive TCR-GR, in 2 patients TCR-GR was not done and the remainder was negative. Twenty out of 24 patients had cytomegalovirus (CMV) viremia confirmed by PCR before the onset of T-LGL expansion; the remainder had no CMV viremia. In all patients with T-LGL expansion there was no subsequent recurrence of CMV viremia or infection. All 24 patients had documented graft versus host disease (GvHD). In the group with T-LGL expansion only 2 patients relapsed with primary disease and only one patient died (due to a cardiac event). The cumulative incidence of T-LGL expansion was 4.4% at the end of the study period. Conclusion: To our knowledge, this is the largest reported series of T-LGL expansion post allogeneic HSCT. T-LGL expansion was associated with an interesting sequence of CMV viremia preceding T-LGL expansion and subsequent lack of recurrence of CMV viremia or infection. We also observed a very low number of relapse of primary disease or death in patients with T-LGL expansion. One hypothesis is that T-LGL expansion may be a result of specific stimulation with CMV antigens post allogeneic HSCT. An alternate hypothesis is that T-LGL expansion is a surrogate marker for accelerated immune reconstitution. At present, it is also unclear if T-LGL expansion is a marker of ‘graft-versus-leukemia' effect with respect to relapse of primary disease warranting further research. Disclosures: Lum: Transtarget Corporation: Founder