Utility of the FAB classification for myelodysplastic syndromes: investigation of prognostic factors in 237 cases

The utility and prognostic significance of the FAB classification was studied in 237 patients with a myelodysplastic syndrome. No significant differences in actuarial survival and probability of transformation to acute leukaemia were found in patients with RA, AISA or CMML. The median survival time for the RA group was 50 months, for the AISA and CMML subclasses more than 60 months. The probability of transformation for the RA, AISA and CMML subgroups showed a linear trend with a probability of 25% for the RA, 16% for the AISA and of 18% for the CMML groups after a 5 year observation period. A uniformly poor prognosis was found for the RAEB and RAEB/t subgroups with median survival times of respectively 9 and 6 months. Chromosomal abnormalities were found in 68 out of 155 patients (44%). Patients with only normal metaphases or with abnormal metaphases together with karyotypic normal cells had a longer median survival time and a lower probability for transformation as compared to those with only abnormal metaphases. The most important factor in prognosis is the number of blast cells in blood and bone marrow. Age and sex, and certain quantitative and qualitative abnormalities in the peripheral blood appear of limited prognostic value for patients with RA, AISA and CMML. The longer life expectancy of 35 patients with CMML as compared to other series seems to be related to the percentage of blast cells at the time of diagnosis.