Response To Erythroid Stimulating Agents (Esa) And Flow Cytometric Characteristics Of Bone Marrow Erythroid Precursors In Ipss-R Lower-Risk Myelodysplastic Syndrome Patients

Context: Standard treatment of anemia in lower-risk myelodysplastic syndromes (LR-MDS) is based on erythropoietic-stimulating agents (ESAs), but some patients are primary refractory (PR) or lose response (secondary refractory, SR). High serum erythropoietin (sEPO) is the main negative predictor, and treatment of ESA-resistant anemia is challenging, so more predictors are needed. EPO promotes differentiation of committed erythroid cells (COMe) into erythroid precursors (EP), constituted by early (EEP) and late (LEP) precursors. Flow cytometry (FC) can characterize COMe and EP. RED score is an FC parameter that assesses dyserythropoiesis. Objective: We aimed to correlate COMe, EP, and RED score with response to ESAs, WHO category, and sEPO in 44 anemic LR-MDS patients. Design: We evaluated 10 negative controls, 17 PR patients, 17 SR patients, and 10 long responders (LR, response duration >24 months). Fifty-nine percent had sEPO 500 mU/mL(H-EPO); 23% had single lineage dysplasia (MDS-SLD), 34% multilineage dysplasia (MDS-MLD), 23% ring sideroblasts (MDS-RS), and 20% deletion of 5q (MDS-5q-). FC analysis was performed on bone marrow aspirates for all subgroups at diagnosis and within SR subgroup at loss of response to ESA (SRII). We used anti-CD34, CD36, CD105, CD117, CD33, CD71, and CD45 antibodies to identify COMe, total erythroid cells (TOTe), and EP. Coefficients of variance of CD71 and CD36 were used to calculate RED score. Results: TOTe and COMe were increased in LR-MDS compared to controls (p=0.013 and p=0.04, respectively), with the exception of MDS-5q- cases. In the PR subgroup, LEP were increased and COMe were reduced compared to LR. In the SRII group, COMe were lower than at diagnosis (p=0.039). RED score was higher in PR compared to responders (p=0.011). MDS-5q- cases showed reduced TOTe (p=0.047), while MDS-RS cases had higher LEP and RED score (p=0.008 and p=0.012, respectively). Finally, LEP were increased in the H-EPO group compared to L-EPO (p=0.023). Conclusions: These data suggest that COMe seem to be positively associated with ESA response, whereas higher LEP and RED score are negatively associated and also correlate with MDS-RS and H-EPO. Finally, MDS-5q- cases displayed fewer TOTe and COMe, suggesting premature apoptosis of erythroid precursors.