Long-term survival of patients with acute myeloid leukemia: Updated results from two trials evaluating postinduction chemotherapy

BACKGROUND. Although the prospect of long-term disease free survival (LFS) after chemotherapy for acute myeloid leukemia (AML) is widely accepted, few studies have reported long-term survival data. The authors therefore updated results from a 1981 report on a study conducted by the University of Minnesota Masonic Cancer Center (UMMCC) and a 1989 report on a study conducted by the North American Marrow Transplant Group (NAMTG). METHODS. Minimum follow-up of 21.6 years for living patients was obtained for 26 patients who received weekly cytarabine and 6-thioguanine maintenance therapy after achieving complete remission (CR) in the UMMCC study. Minimum follow- up of 7.7 years was obtained on 87 patients treated with high dose cytarabine intensification in first remission in the NAMTG study. RESULTS. In the UMMCC study, the LFS rate was 28% and the overall survival rate was 15%. Nineteen percent of patients died in first CR at 1.3-12 years. Three patients remain alive in initial CR at >20 years. In the NAMTG study, the LFS rate was 49% and the overall survival rate was 45%. A total of 58 patients (44%) remain alive in initial CR at a median of 11.4 years after diagnosis. An additional patient is alive in second CR at 8.6 years after diagnosis. In both studies, relapses after 3 years were relatively uncommon (11-12%). CONCLUSIONS. Chemotherapy alone is curative in more than 40% of AML patients who achieve CR. Short-term, high dose cytarabine intensification appeared more efficacious, without increased toxicity, compared with low dose, prolonged cytarabine-based maintenance. However, for patients who cannot receive intensification, prolonged, low dose maintenance therapy is an acceptable alternative for achieving cure. A minimum follow-up of 3 years is a reasonable predictor of long-term survival and should be obtained in studies evaluating therapeutic outcome in cases of AML.