Hematologic Remission of Chronic Myelogenous Leukemia after Treatment with Imatinib Includes Normalization of the Red Cell Distribution Width.

After treatment with imatinib, the majority of patients with chronic myelogenous leukemia (CML) achieve hematologic remission. This includes normalization of blood counts (red cells, white cells, and platelets) normalization of the white cell differential, and disappearance of abnormal immature cells from the peripheral blood. However, abnormal erythropoiesis may be more subtle than abnormal red cell counts. We reviewed two other indices of erythropoiesis, the mean cell volume (MCV) and the red cell distribution width (RDW). We studied 15 patients with a diagnosis of CML confirmed by BCR-ABL, in whom the first-line therapy was imatinib. Treatment dosage varied from 400 – 800 mg/day. Pre-treatment, all patients had an elevated white cell count, 14 of 15 had a low hemoglobin, and 11 of 15 had an abnormal high platelet count. None had an abnormal MCV (mean, 91.3, range 82 – 97), and 13 of 15 had an abnormal RDW (mean 16.2, range 14.1 – 19.2). After treatment was started, all 15 achieved a normal white cell count, hemoglobin, and platelet count within 3 months. All continued to have a normal MCV, with no apparent change (mean 92.1, range 82 – 98). However, after treatment 14 of 15 developed a normal RDW (mean 13.7, range 12.0 – 15.2). The RDW progressively declined during the first 3 months after treatment and reached an asymptote at that time. We conclude that hematopoiesis normalizes qualitatively as well as quantitatively after successful imatinib therapy of CML. Future study will determine whether an isolated elevated RDW will predict relapse or briefer duration of remission.