MODIFICATIONS OF ERYTHROPOIESIS IN MYELODYSPLASTIC SYNDROMES TREATED WITH RECOMBINANT ERYTHROPOIETIN AS EVALUATED BY SOLUBLE TRANSFERRIN RECEPTOR, HIGH FLUORESCENCE RETICULOCYTES AND HYPOCHROMIC ERYTHROCYTES

Background. The aim of this study was to evaluate changes in erythropo iesis induced in vivo by recombinant erythropoietin (r-EPO) treatment in myelodysplastic syndromes (MDS), by means of some new, non invasive laboratory parameters. Patients and Methods. Serum levels of soluble transferrin receptor (STR), a marker of total marrow erythroid activit y, and automated detection of high fluorescence reticulocytes (HFR) an d hypochromic erythrocytes (HE) (respectively, indexes of effective er ythropoiesis and functional iron deficiency) were longitudinally measu red in 25 MDS patients treated with r-EPO, and then correlated with co nventional clinical and laboratory features. Results. Stimulation of e rythropoiesis was documented in 8 patients, whose serum STR levels sho wed a significant, early (within 16 days) increase during treatment wi th r-EPO. However, only 3 of these patients demonstrated a concomitant rise in HFR, and these were the only subjects who experienced a signi ficant clinical response. Two of these patients also developed a funct ional iron deficiency while on treatment, as documented by an increase in HE, despite normal serum iron, transferrin saturation and even ver y high levels of ferritin. They needed iron supplementation to maintai n the response to r-EPO. No variation in STR, HFR or HE occurred in th e remaining 17 unresponsive patients during at least two months of tre atment. Serum levels of thymidine kinase, an aspecific marker of cellu lar proliferative activity, paralleled those of STR. No correlation wa s found between STR, HFR or HE and serum level of endogenous EPO, hemo globin or transfusion requirements in MDS patients. Conclusions. These findings suggest that there is a heterogeneous and complex pattern of erythroid response in MDS patients treated with r-EPO. In addition, o ur results indicate that STR, HFR and HE may provide useful informatio n for the clinical management of these patients.