NPM1 mutation and progressed rapidly to AML. Diagnosis for all this group of patients was supported with the detection of clonality through the NGS study. • Intermediate-2 and high risk IPSS: 4/5 patients (80%) had abnormal karyotype with monosomy 7. Additionally, all of them had at least a somatic mutation in TP53, RUNX1, EZH2, ASXL1 or NPM1. Patients with NPM1 mutation were treated with intensive chemotherapy. After stem cell transplantation, use of NGS for minimal residual disease monitor- ing has been proposed. • In CMML patients, clonality was detected with NGS in 4 out of 5 patients, one of them carrying a mutation in JAK2 and IDH2 and another in ASXL1 and SRSF2. Conclusions: NGS has a promising role in diagnosis and prognosis in MDS, especially in those patients with normal cytogenetics. Follow-up, treatment and monitoring algorithms can also be assisted by NGS, including anticipated or targeted treatments. 180 IS THE DIAGNOSIS OF PATIENTS WITH DEL(5Q) AND TRISOMY 8 DIFFERENT, WHEN FOUND IN UNRELATED CLONES OR IN ONE CLONE? R. Neuwirtova 1 , Z. Zemanova 2 , M. Belickova 3 , P. Dvorak 4 , J. Cermak 3 , V. Vozobulova 5 , L. Cervinek 6 , A. Jonasova 7 1 Dept of Hematology, 1st Dept of Medicine – Charles University Hospital, Prague 2, Czech Republic; 2 Oncocytogenetic, Oncocytogenetic Charles University Hospital, Prague, Czech Republic; 3 Hematology, Institute of hematology and blood transfusion, Prague, Czech Republic; 4 Medical Cytogenetic, Medical cytogenetic University hospital Plzen, Plzen, Czech Republic; 5 I. Medical Clinic, Univeristy Hospital Plzen, Plzne, Czech Republic; 6 Hematooncology Clinic, University Hostital Brno, Brno, Czech Republic; 7 Dept of Hematology, 1st Dept of Medicine- Charles Univeristy Hospital, Prague, Czech Republic We analysed clinical data, laboratory findings (including normal or increased thrombocytes), prognosis and survival of 16 patients with del(5q) and trisomy 8 in two unrelated clones and compared them with typical 5q- syndrome. All l6 pts were women. They comply with 5q- syndrome criteria, which is illustrated by the following description of their disease course. One woman lives with mild anemia without any treatment, one patient with intermittent 5–6% blasts is living on transfusions and Fe chelatation. One woman was successfully transplanted with compatible brothers´stem cells, two polymorbid patients died from non hematological causes after 3 and 11 years respectively. One patient responded to repeated imunosuppressive therapy but after 20 years developed RAEB2 without response to azacitidine and died. Nobody developed AML. 10 patients were treated with lenalidomide, all with positive response. One patient with TP53 mutation later stopped responding to lenalidomide and is again transfusion dependent. Two patients experienced late relaps of anemia, but under ongoing lenalidomide their blood count again normalized aftererythropoietin application, in one patíent till after addition of steroids. Two biclonal patients reached cytogenetic remission, in one of them with disappearance of both aberrations, in the other only del(5q) disappeared. The size of trisomy 8 clone was smaller than 5q- clone in all biclonal patients except one but its size never showed any significance for the patients’ outcome. We are not able to state precize incidence of biclonal patients, it can be estimated between 5% and 9%. The observation of the clinical characteristic and outcome of our 16 patients entitles us to diagnose patients with del(5q) and trisomy 8 in two unrelated clones as the subgroup of 5q- syndrome. While patients with two unrelated clones have favorable prognosis and long survival, patients with both aberrations in one clone of cells create quite different group of MDS patients. The analysis of our 5 patients with del(5q) and trisomy 8 in one clone shows that these patients belong to high risk MDS, have short survival, transform to AML and demand quite different choice of therapy. Therefore in patients with del(5q) and trisomy 8, it is absolutely necessary to find out whether these two aberrations are in two unrelated clones or in one clone of cells. 181 SF3B1 MUTATION IN LOW-RISK MDS: IMPACTOF ITS INCORPORATION TO THE UPDATED 2016 WHO CLASSIFICATION AND RELATIONSHIP WITH FERRIC OVERLOAD S. Redondo Velao 1 , C. Martinez Laperche 2 , J. Suarez 3 , M. Chicano 3 , N. Ferrnandez 1 , D. Carbonell 3 , I. Buno 2 , J.L. Diez-martin 4 , P. Font Lopez 1 1 Department of Hematology and Hemotherapy, Hospital General Universitario Gregorio Marañón- Madrid-Spain, Madrid, Spain; 2 Department of Hematology and Hemotherapy, Hospital General Universitario Gregorio Marañón- Madrid-Spain- Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; 3 Department of Hematology and Hemotherapy, Hospital General Universitario Gregorio Marañón- Madrid-Spain-Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; 4 Hospital General Universitario Gregorio Marañón- Madrid-Spain-Instituto de Investigación Sanitaria Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain Introduction: The SF3B1 somatic mutation, which encodes an essential ribonucleo-protein in the splicing of RNA, is associated with ring sideroblasts (RS) and correlates with a favorable prognosis. 2016 WHO classification extends the MDS-RS category to cases as fewas 5% RS if the mutation is identified. The high prevalence of SF3B1 in refractory anemia with RS and thrombocytosis converts this category into a definitive entity called MDS/MPN-RS-T. It is postulated that patients with SF3B1 mutated have a parenchymal iron overload, because they present ineffective erythropoiesis and probable it is associated with downregulation in iron homeostasis. Our objective was to reclassify patients according 2016 WHO, as well as to study the characteristics that the mutation confers. Methods: We retrospectively analyzed 45 patients (39 low-risk MDS and 6 MDS/MPN-RS-T) with <5% bone marrow blasts and very low and low-risk according to the IPSS-R classification. They were diagnosed in our center from 2003 to 2016. We determined by conventional PCR and Sanger sequencing the SF3B1 mutation. Results: SF3B1 mutated was detected in 30/45 (67%) patients (Poster Table 1). The most prevalent mutation in 57% of cases was K700E (change from one Adenine to one Guanine) in exon 15, and the rest were located in exon 14. The SF3B1 mutation allowed to reclassify 3 patients with refractory cytopenia with multiline dysplasia and without RS, such as MDS-RS with multilineage dysplasia (3/39, 8%). All patients with MDS/ MPN-RS-T carried the mutation. No patient with single lineage dysplasia (MDS-SLD) exhibited the mutation. SF3B1 was significantly associated with the presence of RS and higher neutrophil and platelet counts (Poster Table 2). Patients with mutated SF3B1 and transfusional dependence had a higher annual transfusion rate and greater iron overload defined by ferri- tin >1,000 μ/L and 100% transferrin saturation, without statistical significance. The use of chelators was uncommon in both groups. With a median follow-upof 4 years, the overall survival (OS) at 3 years was 87%. Twelve patients died, 2 due to progression of the disease. There were no statistically significant differences in OS neither in event free survival. Conclusions: In our experience, SF3B1 mutation allowed us to reclassify 8% of patients in a better prognostic group, according Poster Presentations – 14th International Symposium on Myelodysplastic Syndromes / Leukemia Research 55 S1 (2017) S45–S167 S111