Monitoring DNA cytometric parameters during the course of chronic myelogenous leukemia

The prognostic value of three DNA cytometric parameters - stemline ploidy (STL), stemline shoulder fraction (SSF) and ''proliferative'' fraction (PRF) - for the prediction of disease transformation and survived was examined for 20 patients with chronic myelogenous leukemia (CML) during the course of their disease and compared with two commonly used hematologic parameters (degree of leukocytosis and percentage of circulating leukemic progenitor cells). With disease progression, STL and SSF increased significantly, whereas PRF showed a steady decrease from diagnosis to blast crisis. The most significant part of these changes took place during the chronic phase, before the clinical onset of disease transformation. Hematologic parameters, in comparison, revealed significant changes later, shortly before blast crisis. The remaining duration of the chronic phase diminished from 25.5 months at the time of diagnosis, when the median STL was 2.0c, to 19.6 months for patients showing an STL of 2.1c, to 15.0 months with an STL of 2.2c and to 1.0 months for those with an STL of ≥2.3c. Prognostically relevant limits for SSF and PRF were at 20%. When the SSF passed this limit or the PRF fell below it, the mean remaining chronic phase of these patients amounted to only 14.1 and 10.1 months. Interactive cytometry allows analysis of the DNA cytometric equivalent of changes in leukemic progenitor cells, which are well known from cytogenetic and cell kinetic studies. These three DNA cytometric parameters reflect the ''natural history'' of CML with the development of a cytogenetically hyperdiploid clone during disease progression in most patients and a simultaneous loss of proliferative potential on the level of myeloblasts. They might offer continuous cytometric parameters for monitoring the individual patient's risk of blast crisis.