Prevention of chemotherapy-induced leukemia and of leukemia relapses.

Fifty percent of patients with the myelodysplastic syndrome, frequently following treatment by radiation or chemotherapy, have prognostically unfavorable deletions of the long arms of chromosomes 5 and 7, or trisomy 8, as have the 25% of patients with acute myeloblastic leukemia where remissions last 6-12 months, and where relapse cannot be prevented. In contrast, patients with prognostically favorable cytogenetics (translocation 15; 17 or 8; 21 or inversion 16) maintenance chemotherapy may prevent relapses. Of chronic myelocytic leukemia patients, 85% can achieve hematological remission with interferon alpha, and 40% a partial cytogenetic remission, which probably delays relapse.