Post-Transplant Platelet Recovery Kinetics and Its Association with Overall Survival in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplant (HSCT)

Abstract 2049 Background: Post-transplant thrombocytopenia is universal among recipients of hematopoietic stem cell transplantation (HSCT). We have previously reported a secondary post-transplant thrombocytopenia following autologous HSCT which is associated with poor survival (Ninan MJ, et al., BBMT 2007), however the clinical significance of a fall post-engraftment in platelet counts among recipients of allogeneic HSCT has not been studied. Methods: A total of 929 consecutive pts who underwent allogeneic HSCT between 1993 and 2009 were studied in an IRB-approved retrospective analysis. 55% of pts were male and 45% were female with a median age of 43 ± 12.6 years. Diagnoses included: acute leukemia (423, 46%), chronic leukemia (197, 21%), non-Hodgkin9s lymphoma (110, 12%),myelodysplastic syndrome (93, 10%), multiple myeloma (26, 3%), and other less common malignancies (80, 8%). Disease status was classified into five different categories: complete remission (287, 31%), partial remission (297, 34%), refractory (180, 19%), untreated (28, 3%) and incompletely classified (137, 15%). Grafts were obtained from related donors in 595 pts (64%), and unrelated donors in 334 pts (36%), with 55% peripheral blood stem cell (PBSC), 42% bone marrow (BM), and 3% cord blood units or multiple sources. Blood platelet counts and platelet transfusions were collected from 15 days pre-transplant until 100 days post-transplant. Platelet engraftment was defined as a platelet count ≥ 50 x10E3/mcL without a platelet transfusion in the previous 7 days. Pts (n=816) who achieved platelet engraftment and survived at least 30 days were selected for further analysis. Results: The 816 evaluable pts were divided into cohorts based upon their post-transplant survival: 146(18%) who died within 100 days post-transplant (early death); 267 (33%) that survived 100 days −2 years post-transplant (late death), 319 (39%) who survived > 2 years (long-term survival), and 84 (10%) were lost of follow-up within the first 2 years. Transfusion-independent platelet engraftment was achieved at median of 15 days post-transplant with no significant differences seen in the kinetics of initial engraftment among the different pt cohorts. Median platelet counts at different time points post-transplant were plotted for each pt cohort (Figure 1). Pts in the early-death cohort had a continuous decline in median platelet counts from engraftment values of > 50 x10E3/mcL to a median values of ∼20 x10E3/mcL. Univariate analyses indicated that higher platelet counts at day −15 (prior to conditioning) or at day 100 post-transplant were significantly associated with improved overall survival (HR of 0.63 and 0.39 respectively, P 80 × 10E3/mcL on day +100 had 5 year survival of more than 50% compared with 30% survival in the pt cohort with platelet counts Conclusion: Pts with continuously low platelet count after initial platelet engraftment are at high risk for early death. Higher pre-transplant platelet may be a surrogate for disease status and extent of prior therapy and are associated with long-term survival among pts undergoing allogeneic HSCT. Post-transplant thrombopoiesis at day 100 is highly correlated with long-term survival after allogeneic HSCT, identifying a high-risk group of transplant pts for whom additional treatment strategies are needed. Disclosures: Gleason:Celgene, Merck, Millenium: Consultancy.