Relapsing process in FAB subtypes of adult acute leukemia and its relationship to treatment regimens

The relapsing process in the bone marrow was studied in those 77 patients with adult acute leukemia, diagnosed according to the FAB classification who achieved complete remission (CR) and then received intermittent multi-drug intensification treatment. Relapse occurred in most of the patients who exhibited Auer rods or Ph1 chromosomes in the bone marrow, or in whom blasts increased to 8% or more, but some patients remained in CR by subsequent treatment, that is, relapsing process was reversible. With our conventional treatment, the relapse or relapsing process occurred in most of the patients with L1, L2 and M1 subtypes within 6 months and was irreversible. It occurred mainly between 5 and 13 months in those with M2, M3 and M5 and was reversible in some cases. Patients with M4 subtype received intensified treatment due to the difficulty of achieving remission; relapse was seen in only 3 of 7 cases. To prevent relapse and attain a potential cure, the treatment should be intensive before the relapsing process with adequate supporting care. In view of the above-mentioned observations, our new treatment protocols for acute leukemia were designed to be more intensive than those conventionally employed, and to be discontinued within approximately 10 months in lymphoblastic leukemia and approximately 8 months in myeloid leukemia.