Colony-cluster ratio and cluster number in cultures of circulating myeloid progenitors as indicators of high-risk myelodysplasia.

Circulating myeloid progenitors were assayed in 172 normal subjects and 147 patients with myelodysplastic syndrome (MDS). Patients whose cultures had colony/cluster ratios (CCR) less than 0.3 had significantly shorter survival periods than comparable patients with CCR greater than 0.3. A second prognostic indicator, which complemented CCR, was identified in patients with less than 5% blasts. Median survival was significantly reduced in patients with greater than 15 clusters/ml blood despite colony and cluster numbers being predominantly within the normal range. Characteristic differences were found in three FAB groups large enough to allow statistical analysis. Survival amongst patients with refractory anaemia with excess of blasts (RAEB) was related to CCR and was independent of cluster number. Amongst sideroblastic patients (SA) survival related only to cluster number. Refractory anaemia (RA) patients included individuals in both high-risk groups with only three patients out of 64 showing both features. Amongst all the MDS patients, those with CCR greater than 0.3 and less than 15 clusters/ml blood formed a low-risk group (n = 60) with a relatively good prognosis of whom 85% survived the study period (median duration 938 d) including 94% of those in this group with less than 5% marrow blast cells.