A simplified in vitro classification for prognosis in adult acute leukemia: the application of in vitro results in remission predictive models

Previous classification in vitro of adult acute leukemia incorporating morphology has been complex and difficult to understand. We have devised a simplified classification based solely on leukemic proliferation in vitro. Seventy six patients with adult acute leukemia previously untreated were included in this study and received identical chemotherapy. Three groups were recognized. The complete remission rate was 76% in the 21 patients with no leukemic growth in vitro (Group 1), 75% in 36 patients with leukemic cell growth but aggregates of 20 cells or less (Group 2), and only 21% in the 15 patients with aggregates of greater than 20 (Group 3). There was a highly significant difference in complete remission rates between Group 3 and the other two groups (p < 0.001). Linear logistic regression analysis demonstrated the independence of the growth in vitro from other prognostic variables. A predictive model utilizing the in vitro result more accurately predicted for remission, both retrospectively and prospectively, than a model constructed with presently known prognostic parameters. The cause of death in failures suggested that this system detects resistance to the chemotherapy.