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RESEARCH PRODUCT

Outcome of Refractory Anemia with Ringed Sideroblasts Associated with Marked Thrombocytosis (RARS-T) In a Large Cohort of Patients

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Abstract Abstract 4113 Introduction: Most of the data related to RARS-T, a rare disorder, involve small cohorts of patients. We aimed to analyze more patients also considering a variety of myelodysplastic or myeloproliferative disorders. Objective: To compare a large cohort of patients with RARS-T to refractory anemia with ringed sideroblasts (RARS), refractory anemia with ringed sideroblasts and multilineage dysplasia (RARS-MD) or essential thrombocythemia (ET) at the time of diagnosis and during disease evolution, in terms of survival and complications. Materials: Data of a European multi-center study was used including 199 cases of RARS-T 173 cases of RARS, 102 cases of RARS-MD and 431 cases of ET. Results: At baseline, compared to RARS and RARS-MD patients, RARS-T patients had similar hemoglobin concentration, but a higher white blood count. The JAK2V617F mutation was observed in 43%, 12% and 5% in RARS-T, RARS and RARS-MD patients, respectively. When separated in 2 groups (450,000<platelet count <600,000 and platelet count >600,000 × 109/l), RARS-T patients were comparable for sex, age, hemoglobin level and survival. However, patients with platelet count > 600,000 × 109/l had higher WBC (11 ×109/l versus 7.5 ×109/l, p<0.001). Similarly, no difference was noted in the survival in the JAK2 positive and negative RARS-T patients. The age and sex standardised overall survival of RARS-T patients was similar to RARS and RARS-MD patients, but lower than ET patients (p<0.001). This was despite a higher risk of transformation in acute leukemia, relative to RARS-T afflicted individuals, of 2.4 and 3.5 in RARS-MD and RARS patients, respectively. Conclusion: According to our results, the outcome in RARS-T more closely mimics myelodysplastic syndromes rather than myeloproliferative neoplasms. Our results agree with the WHO 2008 classification that considers RARS-T as a separate disorder. Disclosures: Schnittger: MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Gattermann:Novartis: Honoraria, Research Funding. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.