Autonomous Growth of Blast Cells Is Associated With Reduced Survival in Acute Myeloblastic Leukemia

Abstract

We have previously classified the in vitro growth characteristics of clonogenic blasts from patients with acute myeloblastic leukemia (AML) according to their capacity to proliferate autonomously in a blast cell colony assay. Here we have analyzed whether the presence of in vitro autonomous growth characteristics has any clinical relevance in AML. We have studied 50 patients (age 2 to 64 years), all of whom were treated with combination chemotherapy, excluding patients with a history of antecedent myelodysplasia. Leukemic cells from 34 of 50 patients (68%) exhibited either partial or totally autonomous growth in a blast cell colony assay. Cells from the remaining patients exhibited nonautonomous growth and were either totally dependent on exogenous growth factor (n = 8) or failed to proliferate at all in the culture system used (n = 8). All 50 patients were treated by intensive chemotherapy and 69% achieved complete remission (CR). Patients whose blasts exhibited autonomous growth in vitro had a significantly lower CR rate (57%) compared with the 16 patients with nonautonomous growth (94%, P = .02). White blood cell count was the only other significant factor (P = .03), but in multivariate analysis growth characteristics remains the most important predictor of CR. Actuarial relapse risk is 80% and 42% at 5 years for autonomous and nonautonomous groups respectively (P = .1). Overall disease-free survival is 21.8% and is higher in the nonautonomous growth group at 54.2% compared with 11.3% at 5 years (P = .0015) in the autonomous growth characteristics was found to be the single most important indicator of CR and disease-free survival. Our data suggests that the suppression of autocrine growth factor production may be of value in the treatment of AML.