Anthracycline-based therapy of de novo acute myeloid leukemia in adults: failure of first-cycle cytoreduction to predict second-cycle outcome.

During 1971-1988, 194 adults with de novo acute myeloid leukemia (AML) received initial therapy at the University of Minnesota with an anthracycline-based regimen. Seventy-two of the 194 required further chemotherapy and received a second cycle of the same or similar therapy; 63 of these 72 were evaluable. For each marrow, a tumor burden index (TBI) was calculated, as the product of the marrow cellularity and the proportion of malignant cells. For each patient, the decrement in TBI between the initial and day approximately 14 marrows was recorded. Patients who achieved second-cycle CR were comparable to those who did not in general descriptors; there was no difference between second-cycle CR achievers and nonachievers in the cytoreduction effected by the initial cycle of therapy (74.9% +/- 4.5% [sigma] versus 71.9% +/- 5.9%). We then stratified patients according to the first-cycle cytoreduction, asking if we could find a level that was reliably predictive of increased or decreased likelihood of achieving CR with cycle 2. We could not, despite testing at many centile cuts. Patients achieving a very "poor" degree of cytoreduction in cycle 1 were as likely to achieve CR with cycle 2 as were patients having a very "good" initial cytoreduction. We conclude that (1) first-cycle response is not a useful predictor of second-cycle outcome in anthracycline-based therapy of de novo adult AML; and (2) a "poor" response to cycle 1 does not therefore a priori indicate a change to a different regimen for cycle 2.