Peripheral blood lymphocyte and monocyte recovery and survival in acute leukemia postmyeloablative allogeneic hematopoietic stem cell transplant

Many previous studies of immune reconstitution (IR) postallogeneic hematopoietic stem cell transplantation (HSCT) have focused on lymphocyte recovery. Recognizing that IR involves complex interactions between innate and adaptive immune networks, we hypothesized that patterns of both monocyte and lymphocyte recovery could provide additional prognostic information. To test our hypothesis, we analyzed data from 135 consecutive patients undergoing myeloablative allogeneic HSCT for acute myeloid (AML) and lymphoblastic leukemia (ALL) from 2001 to 2010. The absolute lymphocyte and monocyte counts (ALC and AMC, respectively) were determined longitudinally at days +15, +30, +60, and +100, and correlated with clinical outcomes. At the day +30 time point, both ALC and AMC >0.3 × 10⁹ cells/L were strongly associated with improved survival (overall survival [OS] 29.6 months versus 5.4 months, P = 006 and 25.3 months versus 5.1 months, P = 01 respectively), a pattern that generally continued through the day +100 evaluation. Multivariate analysis revealed the following independent prognostic factors: early disease status at transplantation, the development of chronic GVHD, the day +30 AMC, day +100 AMC, and day +100 ALC. To further explore whether any inherent patterns in the timing of lymphocyte and monocyte recovery had prognostic value post-HSCT, we performed unsupervised hierarchical clustering on the longitudinal hematopoietic parameters studied in this cohort. Four clusters of patients were identified: clusters A-D. Patient clusters B and D both demonstrated improved ALC and AMC recovery at the day +60 and day +100 time points and had significantly improved OS compared with clusters A and C (57.8 months versus 19.7 and 4.4 months, respectively, P < 001). Our data suggest that patients with poor lymphocyte and monocyte recovery beyond the day +60 time points may be at risk for poorer outcomes, and that further investigation into lymphoid/myeloid interactions in developing individualized immunotherapy is warranted.