Recognition of drug resistance during remission induction therapy for acute non-lymphocytic leukemia: utility of day 6 bone marrow biopsy.

While the majority of patients under 70 years of age with acute non-lymphocytic leukemia enter remission when treated with a combination of cytosine arabinoside and an anthracycline antibiotic, 20-45% of patients do not. The reasons for treatment failure in these patients vary from drug resistant disease to death from infection or bleeding shortly after remission induction therapy is initiated. Clearly, more intensive remission induction therapy should be administered only to those patients for whom the therapy being employed is of insufficient intensity. Bone marrow biopsies after six days of therapy have been performed on 53 patients who received 65 courses of remission induction therapy. Eighty-eight per cent of the remissions occurred in patients whose marrow cellularity was less than 62.5% on day 6 while 78% of patients who had drug resistant disease had day 6 marrow cellularities which exceeded 62.5%. Hence, a bone marrow biopsy performed after six days of therapy permits the recognition of the majority of patients who will enter complete remission or alternatively who need more aggressive therapy.