Early lymphocyte recovery at 28 d post-transplant is predictive of reduced risk of relapse in patients with acute myeloid leukemia transplanted with peripheral blood stem cell grafts

Allogeneic hematopoietic cell transplantation (HCT) is potentially curative for acute myeloid leukemia (AML). Impact of lymphocyte recovery on post-transplant outcomes has been suggested but reports are conflicting. We evaluated the impact of lymphocyte recovery at 28d post-HCT in 191 AML patients using peripheral blood stem cells as graft. Patients were divided into those with absolute lymphocyte count (ALC) 0.5x10(9)/L (n=111, 58%; high ALC group) and those with ALC <0.5x10(9)/L (n=80, 42%; low ALC group), at day 28 post-transplant. With a median follow-up of 49months, overall survival (OS) was significantly improved in the high ALC group (59% at 3yr) vs. patients with low ALC (40% at 3yr, P=0.03). Cumulative incidence of relapse (CIR) was significantly lower in the high ALC group (16% at 3yr) vs. low ALC group (36% at 3yr, P=0.001). Multivariable analysis for CIR demonstrated high ALC group as an independent factor decreasing relapse risk (P=0.03, HR=0.49, 95% CI=0.26-0.92). Multivariable analysis for OS and non-relapse mortality did not demonstrate ALC 0.5x10(9)/L at 28d post-transplant to be predictive. We conclude that lymphocyte recovery with ALC 0.5x10(9)/L at day 28 post-transplant is associated with less relapse in AML patients undergoing allogeneic peripheral blood HCT, but without survival benefit.