Low Dose Cytosine Arabinoside Regimen for Overt Leukemia, Hypoplastic Leukemia and Myelodysplastic Syndromes : Hypoplastic Leukemia Responds Best.

In a series of 38 patients consisting of 13 with overt acute leukemia, 14 with hypoplastic leukemia, and 11 with myelodysplastic asyndromes (MDS), responsiveness to low dose cytosine arabinoside (LDAC) regimen was investigated to clarify the disease type most benefitted. LDAC was continuously administered intravenously at dose 0.2mg/kg/day and continued as long as possible to meet the pre-assigned target point of 5% marrow blasts which was confirmed by weekly marrow aspiration. Overall response rate was 47%; complete remission (CR) being 31% and partial remission (PR) 16%. CR rate was significantly different between the disease types ; 69% in hypoplastic leukemia, 23% in overt leukemia and 0% in MDS (p=0.01). In hypoplastic leukemia the survival time was significantly longer in the LDAC-treated cases compared with 15 historical control cases treated with supportive care only ; median survial being 750 days in the former and 250 days in the latter (p=0.01). In overt leukemia only three M2 AML cases obtained CR ; two of them were treated during hypoplastic phase induced by intensive chemotherapy. All CR cases eventually achieved the target point after 20 to 42 days (median 26) of LDAC administration. Substantial toxicity of LDAC was evident, but most cases tolerated well. The present investigation suggests that hypoplastic leukemia is the disease type most sensitive to LDAC regimen. Stratification of the elderly leukemia patients should be considered for this regimen.