Efficacy of Lenalidomide in Myelodysplastic/Myeloproliferative Neoplasms with Ring Sideroblasts

Background: Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) with ring sideroblasts and thrombosis (MDS/MPN-RS-T), include the dysplastic features of Refractory Anemia with Ring Sideroblasts (RARS) and the myeloproliferative features of essential thrombocythemia (ET) and are characterized by a high rate (50%) of JAK2 V617F mutations or rarely by the presence of mutations in exon 10 of the MPL (myeloproliferative leukemia) gene or in exon 9 of the calreticulin gene. We previously demonstrated that RARS-T differed from RARS and ET from a clinical, biological and prognostic point of view and that the presence of high rates of splicing factor 3B subunit 1 (SF3B1) mutations in RARS-T and the absence of these mutations in ET strengthened the hypothesis that RARS-T was a distinct entity. We also reported in a large series of patients (n=200) that the risk of thrombosis was higher in RARS-T than in RARS patients without a high platelet count, leading clinicians to reduce the platelet count in almost 33% of RARS-T patients. However, due to the presence of anemia, the use of the cytoreductive agents usually used in ET is limited since they worsen the cytopenia. This explains why it is difficult to treat patients who harbor both anemia and thrombocytosis.