Identification of early relapsing patients with adult acute nonlymphocytic leukemia by bone marrow biopsy after initial induction chemotherapy.

Bone marrow biopsies obtained from 69 adult patients with acute nonlymphocytic leukemia (ANLL) six to 10 days after initial induction chemotherapy were reviewed blindly to detect the presence of residual leukemia. Discrimination between the presence or absence of leukemic cells was provided by assessment of the numbers, clustering, and nuclear morphology of blasts and promyelocytes. Twenty-six patients had frank leukemia, 25 had no apparent leukemic cells, and 18 had focal residual leukemia. Of 25 patients whose bone marrow contained no detectable residual leukemic cells, 21 gained complete remission without further chemotherapy. These patients had a median duration of remission of 278 days, with five patients still remaining in remission for 578-882 days. Similarly, all of the 18 patients who had focal residual leukemia achieved complete remission without additional chemotherapy; however, all have relapsed with a median duration of remission of 163 days. This study indicates that patients with foci of residual leukemia in their one-week posttreatment bone marrow samples readily achieve remission, but carry a substantial leukemic burden that increases the likelihood of early relapse.