OBJECTIVETo explore the kinetics of platelet reconstitution and its prognostic significance in patients received unmanipulated haploidentical stem cell transplantation (Haplo-HSCT) without in vitro T cell depletion.

METHODSA total of 291 patients received Haplo-HSCT without in vitro T cell depletion between January 2007 to December 2008 were retrospectively reviewed. They were categorized into 3 groups according to the platelet count on day 30, day 60 and day 90: (1) persistent thrombocytopenia (Group A) was defined as the platelet count never reached 50×10⁹/L on the three time points; (2) unstable thrombocytopenia (Group B): the platelet count recovered to a level of 50×10⁹/L by day 30 or 60 or 90, yet did not reach a level of more than 100×10⁹/L; (3) non-thrombocytopenia (Group C): the platelet count was higher than 100×10⁹/L on day 90. The kinetics of platelet reconstitution, overall survival (OS) and treatment related mortality (TRM) were compared between 3 groups.

RESULTSOf the 291 consecutive patients, 288 cases engrafted successfully and 262 cases were platelet transfusion independent. The median intervals of neutrophil and platelet engraftment were 13 (9-29) days and 17 (7-180) days, respectively. The cumulative incidence of grade III-IV acute graft versus host disease (GVHD) on day 100 and chronic GVHD at 3 years were 14.7% and 56.4% respectively. OS and TRM at 3 years were 64.6% and 22.3% respectively. At the end of the follow-up, 266 cases were platelet transfusion independent: including 71 (24.4%) cases in Group A, 147 (50.5%) in Group B and 73 (25.1%) in Group C. OS in group A, B and C was 38.0%, 69.4% and 80.8% (P<0.05) respectively. TRM in Group A, B and C was 53.5%, 17.7% and 1.4% (P<0.05) respectively. Persistent thrombocytopenia was related with lower OS and higher TRM in multivariate analysis.

CONCLUSIONPersistent thrombocytopenia was common after Haplo-HSCT without in vitro T cell depletion, and patients with persistent thrombocytopenia have poor OS and higher TRM.