Relationship of megakaryocyte size at diagnosis to chemotherapeutic response in children with acute nonlymphocytic leukemia.

Small megakaryocytes are frequently seen in patients with acute nonlymphocytic leukemia (ANLL). In this study, median megakaryocyte diameters were determined in marrow biopsy specimens of 32 children at diagnosis of ANLL and related to platelet count and chemotherapeutic response. The association between median megakaryocyte size and time-to-failure was striking. Seven of 9 patients with median megakaryocyte diameters greater than 20 microns remain in continuous complete remission for more than 3 yr, whereas 20 of 23 patients with smaller median megakaryocyte diameters failed therapy within 15 mo (p = 0.002). By Cox-regression analysis, megakaryocyte size had independent prognostic value (p less than 0.001), surpassing that of spleen size, the only other feature having significant association with time-to-failure. Megakaryocyte size at diagnosis may be useful for predicting the likelihood of prolonged complete remission in ANLL.