LOW-DOSE ARA-C IN MYELODYSPLASTIC SYNDROMES (MDS) AND ACUTE-LEUKEMIA FOLLOWING MDS - PROPOSAL FOR A PREDICTIVE MODEL

Patients with myelodysplastic syndromes (MDS) comprise an extremely heterogenous group. There is a need for decision models both for predicting the natural course of the disease and the outcomes of different treatment alternatives. In 102 consecutive patients with MDS or acute myelogenous leukemia (AML) following MDS, pre-treatment variables were studied in relation to the response to treatment with low-dose ara-C. Thirty patients (29%) responded with either a complete remission or a significant rise in the hemoglobin level. For the remaining 71%, the treatment was ineffective and in some cases hazardous. The factors associated with a poor response to treatment could be divided into two groups: one included low platelet counts and the presence of chromosomal aberrations, both signs of progressive MDS with a short survival, and the other comprised morphological findings, indicating ineffective hemopoiesis. Patients with platelet counts > 150 x 10(9)/l had a response rate of 55%, compared to 24% in patients with subnormal platelet counts. Logistic regression identified low bone marrow cellularity, absence of ring sideroblasts and <2 chromosomal aberrations as predictors of a favourable response in patients with platelet counts < 150 x 10(9)/l. These factors and the platelet count were combined in a predictive model which divided patients into dime groups with different probabilities of response: one favourable (38% of the patients), with a response rate of >50%; a second, intermediate group (33% of the patients), with a response rate of 24%; and a third, unfavourable group (29% of the patients) with only 3% responses. While low-dose ara-C is an effective treatment for some patients, it is ineffective and hazardous for others. We propose a model that can facilitate therapeutic decision-making in 2/3 of patients with MDS and MDS-AML by identifying diose who should not be treated with low-dose ara-C as well as those with a relatively high probability of response.