The treatment of patients with newly diagnosed poor prognosis acute myelogenous leukaemia: response to treatment and treatment failure.

The failure of poor prognosis patients with newly diagnosed AML to enter remission is usually due to two phenomena: a high mortality rate and resistance of the leukaemia to chemotherapy. We conducted a pilot study of a regimen designed to overcome these two types of treatment failure. Patients were carefully selected for therapy on the basis of their likelihood of surviving. Chemotherapy consisted of high dose cytosine arabinoside (HDaraC) with the doses modified on the basis of patient age so as to reduce the risk of toxicity. Finally, daunorubicin was administered only to those patients for whom HDaraC was not likely to produce sufficient antileukaemia effects to produce a remission. The median patient age was 67 years and 69/88 (78%) patients had a history of preleukaemia and/or toxic exposure. Only 11/84 (13%) patients died during remission induction therapy and 40/84 (48%) entered CR. Patients with only one risk factor had a higher CR rate than those with more than one risk factor (56% v. 30%, P = 0.02) and also had longer durations (222 d v. 113.5 d, P = 0.035). Two types of resistance to chemotherapy were observed: 'classical resistance' (the failure of chemotherapy to produce substantial killing of leukaemia cells) and the rapid regrowth of leukaemia cells subsequent to a level of cytoreduction which otherwise would have been sufficient to produce a CR.