INDUCTION FAILURE IN DE-NOVO ACUTE MYELOGENOUS LEUKEMIA IS ASSOCIATEDWITH EXPRESSION OF HIGH-LEVELS OF CD34 ANTIGEN BY THE LEUKEMIC BLASTS

The prognostic significance of CD34 antigen expression in acute myelog enous leukemia (AML) is controversial. Most studies to date have repor ted on CD34 positivity and not the level of antigen present. In this s tudy of 62 patients with de novo AML, 48 (77%) patients were CD34+ in varying levels (0 - 85 mean channels of fluorescence (MCF)). Forty sev en of 62 were treated with combination chemotherapy and 39 (83%) of th em achieved complete remission (CR). Patients with CD34-blasts were mo re likely to achieve CR; however, this trend was not statistically sig nificant (p = .11). On the other hand, patients with higher levels of CD34 antigen on the blasts were less likely to attain CR (p < 0.001,mu ltivariate analysis), The patients who achieved CR expressed lower lev els of CD34 (0 - 57; median 9 MCF) as compared to those who did not ac hieve CR (15 - 85; median 30 MCF). Of the other antigens tested, parti al or complete absence of CD33 (CD33 absent in greater than or equal t o 25% blasts) correlated with failure to achieve CR (p = 0.0029). Thes e results are in keeping with the hypothesis that more primitive AML b lasts with high levels of CD34 are chemoresistant.