Hodnefield, Janice M.

Abstract Smoldering multiple myeloma (SMM) is characterized by a serum M protein ≥ 3g/dL and/or 10% or more of plasma cells in the bone marrow. However, the definition is not standardized, and it is not known whether both serum M protein levels and bone marrow plasma cell counts are necessary for diagnosis or if one parameter is sufficient. We reviewed the medical records and bone marrows of all patients from Mayo Clinic seen within 30 days of recognition of an IgG or IgA M protein ≥ 3g/dL or a bone marrow containing ≥ 10% plasma cells from 1970 to 1995. This allows for a minimum potential follow-up of 10 years. Patients with end-organ damage at baseline from plasma cell proliferation, including active multiple myeloma (MM) and primary amyloidosis (AL) and those who had received chemotherapy were excluded. A differential of the bone marrow aspirate coupled with the bone marrow biopsy morphology and immunohistochemistry using antibodies directed against CD138, MUM-1 and Cyclin D1 were evaluated in every case in order to estimate the plasma cell content. In all, 301 patients fulfilled either of the criteria for SMM. Their median age was 64 years and only 3% were less than 40 years of age; 60% were male. The median hemoglobin value was 12.9 g/dL; 7% were less than 10 g/dL, but the anemia was unrelated to plasma cell proliferation. IgG accounted for 75%, IgA 22%, and biclonal proteins were found in 3%. The serum light-chain was κ in 67% and λ in 33%. The median serum M spike was 2.9 g/dL; 11% were at least 4.0 g/dL. Uninvolved serum immunoglobulins were reduced in 81%; only 1 immunoglobulin was reduced in 31% and both were decreased in 50%. The urine contained a monoclonal κ protein in 36% and λ in 18% and 46% were negative. The median size of the urine M spike was 0.04 g/24h; only 5 (3%) were > 1 g/24h. The median bone marrow plasma cell content was 15 – 19%; 10% had less than 10% plasma cells, while 10% had at least 50% plasma cells in the bone marrow. Cyclin D-1 was expressed in 17%. Patients were categorized into 3 groups: Group 1, serum M protein ≥ 3g/dL and bone marrow containing ≥ 10% plasma cells (n= 113, 38%); Group 2, bone marrow plasma cells ≥ 10% but serum M protein < 3g/dL (n= 158, 52%); Group 3, serum M protein ≥ 3g/dL but bone marrow plasma cells < 10% (n= 30, 10%). During 2,204 cumulative years of follow-up 85% died (median follow-up of those still living 10.8 years), 155 (51%) developed MM, while 7 (2%) developed AL. The overall rate of progression at 10 years was 62%; median time to progression was 5.5 yrs. The median time to progression was 2.4, 9.2, and 19 years in groups 1, 2, and 3 respectively; correspondingly at 10 years, progression occurred in 76%, 59%, and 32% respectively. Significant risk factors for progression with univariate analysis were serum M spike ≥ 4g/dL (p < 0.001), presence of IgA (p = 0.003), presence of urine light chain (p = 0.006), presence of λ urinary light chain (p = 0.002), bone marrow plasma cells ≥ 20% (p < 0.001) and reduction of uninvolved immunoglobulins (p < 0.001). The hemoglobin value, gender, serum albumin, and expression of cyclin D-1 were not of prognostic importance. On multivariate analysis, the percentage of bone marrow plasma cells was the only significant factor predicting progression to MM or AL.

Abstract This study evaluated the contributing roles of flow cytometric immunophenotyping of blood and bone marrow and immunohistochemical paraffin section staining of bone marrow biopsies in the staging of B-cell malignant lymphoma. Flow immunophenotyping was performed on a marrow specimen in 175 cases; a corresponding blood specimen was also immunophenotyped in 135 of these cases. Morphologic marrow involvement by lymphoma was found in 59 cases; flow immunophenotyping identified 54 cases with a monoclonal B-cell process: morphology-positive/flow-positive (n = 49), morphology-positive/flow-negative (n = 10), morphology-negative/flow-positive (n = 5), and morphology-negative/flow-negative (n = 111). The 10 morphology-positive/flow-negative cases included 5 follicular and 5 large-cell lymphomas with minimal marrow involvement. All 5 morphology-negative/flow-positive cases were from patients with large-cell lymphomas and bulky clinical disease. Because the blood contained the same B-cell clone in 2 of 2 morphology-negative/flow-positive cases studied, blood contamination of marrow may account for these findings. Blood flow cytometric immunophenotyping studies were positive in 32 cases; 30 had marrow involvement by morphology and were from patients with follicular, mantle cell, lymphoplasmacytic, small lymphocytic, or marginal zone lymphomas. From our results, we conclude that (1) bone marrow flow cytometric immunophenotyping is not a cost-effective replacement for good morphologic evaluation in lymphoma staging and that (2) a positive peripheral blood flow cytometric immunophenotyping study when performed in low-grade lymphomas correlates with marrow involvement.

Abstract Abstract 971 Unlike the case in acute myeloid leukemia, there is limited information on the prognostic impact of IDH mutations in myelodysplastic syndromes (MDS). In the current study of 277 patients with MDS, IDH mutations were detected in 34 (12%) cases: 26 IDH2 (all R140Q) and 8 IDH1 (six R132S and two R132C). Mutational frequency was 4% (2 of 56) in refractory anemia with ring sideroblasts (RARS), 12% (16 of 130) in refractory cytopenia with multilineage dysplasia, 14% (2 of 14) in MDS-unclassifiable, 14% (6 of 42) in refractory anemia with excess blasts (RAEB)-1, and 23% (8 of 35) in RAEB-2. Normal karyotype was noted in all but one IDH1-mutated cases and 13 IDH2-mutated cases. Multivariable analysis identified presence of mutant IDH1 (p=0.0004; HR 4.0, 95% CI 1.9–8.8), revised International Prognostic Scoring System (IPSS-R) risk category (p<0.0001), and red cell transfusion need (p=0.002) as independent predictors of inferior survival (Figure 1). In a similar multivariable analysis, mutant IDH1 was the only variable associated with shortened leukemia-free survival (p=0.001; HR 7.0, 95% CI 2.3–20.8). The presence of IDH2 R140Q did not affect overall (p=0.54) or leukemia-free (p=0.81) survival (Figure 2). The current study suggests a powerful adverse prognostic effect for mutant IDH1 in MDS. Disclosures: No relevant conflicts of interest to declare.

This study evaluated the contributing roles of flow cytometric immunophenotyping of blood and bone marrow and immunohistochemical paraffin section staining of bone marrow biopsies in the staging of B-cell malignant lymphoma. Flow immunophenotyping was performed on a marrow specimen in 175 cases; a corresponding blood specimen was also immunophenotyped in 135 of these cases. Morphologic marrow involvement by lymphoma was found in 59 cases; flow immunophenotyping identified 54 cases with a monoclonal B-cell process: morphology-positive/flow-positive (n = 49), morphology-positive/flow-negative (n = 10), morphology-negative/flow-positive (n = 5), and morphology-negative/flow-negative (n = 111). The 10 morphology-positive/flow-negative cases included 5 follicular and 5 large-cell lymphomas with minimal marrow involvement. All 5 morphology-negative/flow-positive cases were from patients with large-cell lymphomas and bulky clinical disease. Because the blood contained the same B-cell clone in 2 of 2 morphology-negative/flow-positive cases studied, blood contamination of marrow may account for these findings. Blood flow cytometric immunophenotyping studies were positive in 32 cases; 30 had marrow involvement by morphology and were from patients with follicular, mantle cell, lymphoplasmacytic, small lymphocytic, or marginal zone lymphomas. From our results, we conclude that (1) bone marrow flow cytometric immunophenotyping is not a cost-effective replacement for good morphologic evaluation in lymphoma staging and that (2) a positive peripheral blood flow cytometric immunophenotyping study when performed in low-grade lymphomas correlates with marrow involvement.

Abstract Abstract 3803 Background: Ring sideroblasts (RS) represent abnormal mitochondrial iron deposits that are commonly present in myelodysplastic syndromes (MDS). The presence of ≥15% RS, by definition (World Health Organization-WHO) is necessary for a diagnosis of a MDS-RS; with refractory anemia with ring sideroblasts (RARS) being a specific morphologic category. RS can also be seen with other morphologic categories such as; refractory cytopenias with multilineage dysplasia (RCMD), MDS-unclassifiable (MDS-U) and refractory anemia with excess blasts (RAEB-1/2). Amongst these categories, RARS is generally believed to have the best survival rate with the lowest risk of leukemic transformation and this has been attributed to the absence of associated dysplasia in more than one lineage. However, it has not been systematically shown whether or not the exact percentage of RS provides additional prognostic information in the context of an accurate morphologic categorization and risk stratification by karyotype or the revised IPSS (IPSS-R). Methods: 200 patients with primary MDS without excess blasts and ≥1% RS were seen at the Mayo Clinic from 1997 through 2007. All patients underwent bone marrow (BM) examination and cytogenetic evaluation at diagnosis and the pathology slides, including iron stains, were centrally re-reviewed to accurately quantify bone marrow (BM) RS percentage and to confirm WHO morphologic categories. Molecular profiling included analysis for IDH1, IDH2, JAK2 and MPL mutations. For the purposes of this study patients were divided into 4 categories based on the RS percentage; <5%, 5–14%, 15–50% and >50%. In addition, each patient was assigned IPSS and IPSS-R prognostic scores at diagnosis and risk stratified by karyotype according to the IPSS-R cytogenetic risk categories. Cox proportional regression method was used for multivariable analysis. Results: Of the overall 200 study patients, 140 (70%) were male and median age was 71 years (range, 17–90 years). At presentation, 34 (17%) patients were red cell transfusion-dependent. There were 56 (28%) patients with <5% RS (RCMD-52, MDS-U-14), 32 (16%) with 5–14% RS (RCMD-29, MDS-U-3), 79 (39%) with 15–50% RS (RARS-43, RCMD-29, MDS-U-2) and 33 (16%) with >50% RS (RARS-13, RCMD-17, MDS-U-3). Three patients (2%) were IDH1 mutant (RARS-1, RCMD-2), 17 (8%) IDH2 mutant (RARS-1, RCMD-14, MDS-U-2), 5 JAK2 V617F (3%) mutant (RARS-2, RCMD-3) and one patient with RCMD had the MPL W515L mutation. At a median follow-up of 33 months, 156 (73%) deaths and 24 (12%) leukemic transformations were documented. Median survivals were 63 months for MDS with >50% RS, 43 months for MDS with 15–50% RS, 35 months for MDS with 5–14% RS, and 14 months for MDS with <5% RS (p=0.005). In univariate analysis, additional risk factors included decreased hemoglobin, decreased platelet count, increased circulating blasts, WHO morphologic categories, red cell transfusion need, IPSS, IPSS-R and cytogenetic risk categories per IPSS-R. On a multivariable analysis only the IPSS-R prognostic score (p<0.0001) and the WHO morphologic categories (p=0.02 for RARS) retained significance. Univariate analysis disclosed significantly inferior leukemia-free survival (LFS) in patients with RCMD, thrombocytopenia, increased circulating blasts, and poor IPSS and IPSS-R prognostic scores. On multivariable analysis once again only the IPSS-R prognostic scores (p=0.02) and WHO morphologic categories (p=0.02) retained their significance. In other words, RS percentage, independent of WHO classification, as a continuous or categorical variable (i.e.: <5%, 5–14%, 15–50% & >50%) did not affect either overall survival or LFS. Conclusions: In MDS without excess blasts, once an accurate WHO morphologic categorization is made based on the presence or absence of multi-lineage dysplasia, there is no additional prognostic value for quantifying bone marrow ring sideroblasts. WHO classification and IPSS-R prognostic scores remain the most important factors in assessing patients with MDS. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2918 Background: Monosomal karyotype (MK) is defined as the presence of two or more distinct autosomal chromosome monosomies or a single autosomal monosomy associated with at least one structural abnormality (Breems DA et al. J Clin Oncol 2008; 26: 4791). In acute myeloid leukemia (AML), MK has been associated with a worse prognosis than otherwise complex karyotype, regardless of the specific type of autosomal chromosome involved (Breems DA et al. J Clin Oncol 2008; 26: 4791). Whether or not these observations also hold true for myelodysplastic syndromes (MDS) is currently unknown. Objective: To determine if MDS with complex karyotype can be prognostically sub-stratified further based on the presence or absence of MK and if prognosis in MDS with MK is in addition affected by the presence or absence of monosomy 7 or monosomy 5. Methods: The Mayo Clinic database for MDS was used to identify consecutive patients with complex karyotype, defined as the presence of three or more numerical or structural cytogenetic abnormalities. World Health Organization (WHO) criteria were used for MDS diagnosis and leukemic transformation (Vardiman JW et al. Blood 2009; 114: 937). Overall and leukemia-free survivals were calculated from the time of initial cytogenetic studies documenting complex karyotype. Results: A total of 127 MDS patients (median age 70 years; 79 males) with complex karyotype were identified. Amongst them, 106 (83%) met the above-stipulated criteria for MK and 21 (17%) had complex karyotype without monosomies. The MK in the 106 patients included monosomy 7 and/or monosomy 5 in 73 cases. The three complex karyotype subsets (i.e. complex without monosomies vs. MK that included monosomy 7 and/or 5 vs. MK excluding monosomy 7 or 5) were not significantly different in terms of age and sex distribution, hemoglobin level, leukocyte or platelet count, bone marrow blast percentage or International Prognostic Scoring System (IPSS) risk score. However, survival was significantly inferior in patients with MK compared to those with complex karyotype without monosomies (p=0.01; HR 1.9, 95% CI 1.1–3.3). Multivariable analysis identified MK (p=0.002), advanced age (p=0.0004), increased bone marrow blast percentage (0.04), but not IPSS risk category (p=0.34), as independent risk factors for survival. Interestingly, there was no difference in survival among MK patients further sub-stratified by the presence or absence of monosomy 7 and/or monosomy 5 (Figure 1). Although not statistically significant, leukemia-free survival was also worse in patients with MK compared to those with complex karyotype (p=0.11; HR 2.7, 95% CI 0.8–9.0); none of the aforementioned variables significantly affected leukemia-free survival. Conclusions: Monosomal karyotype in MDS identifies a prognostically worse subgroup of patients with complex karyotype. Furthermore, in the context of MK, autosomal monosomies other than monosomy 7 or monosomy 5 are prognostically as detrimental. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 460 Background: SF3B1 mutations were recently reported to occur in myelodysplastic syndromes (MDS), especially in the presence of ring sideroblasts (RS) (Papaemmanuil et al. Leukemia Research 2011, Volume 35, Supplement 1, page S18). We sought to accurately define the interaction between SF3B1 mutations, bone marrow morphology, karyotype and prognosis in MDS with ≥15% RS (MDS-RS). Methods: Mayo Clinic databases and cell banks were queried to identify patients with MDS and ≥15% RS (MDS-RS). All study patients were required to have undergone bone marrow examination and cytogenetic evaluation at diagnosis. Pathology slides, including iron stains, were centrally re-reviewed to accurately quantify bone marrow RS percentage and confirm World Health Organization (WHO) morphologic categories. Detailed analysis of clinical and cytogenetic parameters was performed to risk stratify patients according to the revised International Prognostic Scoring System (IPSS-R) (Greenberg et al. Leukemia Research 2011, Volume 35, Supplement 1, page S6). All patients were annotated for their mutational status involving JAK2, MPL and IDH. PCR sequencing was used to identify SF3B1 mutations. Results I: Baseline patient information: The study is currently ongoing; to date, results are availab1e in 88 patients (median age 72 years, 69% males) including 36 (41%) patients with refractory anemia with RS (RARS), 36 (41%) with refractory cytopenia with multilineage dysplasia and ≥15% RS (RCMD-RS), 11 (12%) with refractory anemia with excess blasts (RAEB)-1 and ≥15% RS (RAEB1-RS) and 5 (6%) with RAEB2-RS. Median (range) values were 9.1 g/dL (5.8–15.7) for hemoglobin, 4.1 × 109/L (1.2–35.2) for leukocytes and 164 × 109/L (6–585) for platelets. IPSS-R risk categories were 20% very good, 49% good, 11% intermediate, 3% poor and 16% very poor. Karyotype was normal in 60%, other very good/good risk 16%, intermediate-risk 2%, and poor/very poor in 22%; 14% had monosomal karyotype (MK). Six (7%), four (5%) and zero (0%) patients displayed IDH, JAK2 or MPL mutations. Red cell transfusion need was documented in 27 (31%) patients. Results II: Prevalence and distribution of SF3B1 mutations and clinical correlates: SF3B1 mutations (all heterozygous) were detected in 40 (∼46%) of all 88 study patients: 25 (63%) K700E, 6 (15%) K666N/Q/R, 3 (8%) E622D, 2 (5%) H662D/Q, 2 (5%) Y623C, 1 (3%) R625C, and 1 (3%) T663I. One patient each displayed both SF3B1K700E and IDH2R140Q or SF3B1K700E and JAK2V617F. SF3B1 mutational frequencies were 69% for RARS, 36% for RCMD-RS, 18% for RAEB1-RS and 0% for RAEB2-RS (p=0.0007). SF3B1 mutations clustered with normal (59%) and other very good/good risk (57%) karyotype and were infrequent in poor/very poor karyotype (5%; p=0.0004). Additional significant correlations were noted between SF3B1 mutations and lower IPSS-R risk category (p=0.0004), advanced age (p=0.006), higher platelet count (p=0.0003). Results II: SF3B1 mutations and prognostic relevance in MDS-RS: To date, 68 (∼77%) deaths and 10 (∼11%) leukemic transformations have been documented. Median follow-up for living patients was 82 months. Univariate survival analysis considering all 88 study patients identified the following as strongly significant risk factors: IPSS-R (p<0.0001), WHO morphologic categories (p<0.0001), cytogenetic risk categories (p<0.0001), and transfusion need (p=0.0003). In multivariable analysis, only IPSS-R and transfusion need remained significant. In univariate analysis, the presence of SF3B1 mutations was significantly associated with better overall (p=0.04) and leukemia-free (p=0.03) survival; however, in both instances, significance was completely accounted for by WHO morphologic risk categorization and the morphology-adjusted p values were 0.6 and 0.2, respectively. In other words, when RARS and RCMD were analyzed separately, there was no additional prognostic value from the presence or absence of SF3B1 mutations (Figures 1 and 2; p=0.67 and 0.44, respectively). Conclusions: SF3B1 mutations are prevalent in RARS and RCMD-RS but do not provide additional, WHO morphology-independent or IPSS-R-independent, prognostic information. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 1711 Background: Mutations in genes of the splicing machinery, such as SF3B1, SRSF2 and U2AF35 are common in patients with myelodysplastic syndromes [MDS] (Nature 2011;478:64) and chronic myelomonocytic leukemia [CMML] (Haematologica 2012;Epub). In MDS, SRSF2 gene mutations are an independent risk factor for shortened over-all (OS) and leukemia-free survival (LFS) (Blood 2012;119:3578). In MDS with ring sideroblasts (RS), SF3B1 mutations have a high prevalence (∼50%), but do not influence either, the OS or the LFS (Blood 2012;119:569). We carried out this study to evaluate the prevalence, clinical correlates and prognosis of the aforementioned spliceosome mutations in CMML. Methods: The study included 227 patients with WHO defined CMML who were seen at the Mayo Clinic from 1997 through 2007. All patients underwent bone marrow (BM) examination and cytogenetic evaluation at diagnosis. DNA was interrogated in the three most frequent spliceosome genes with somatic mutations; SRSF2, SF3B1 and U2AF35. Results I: Prevalence and clinical correlates Among the 227 study patients, 153 (67%) were male, median age was 71 years (range, 17–90 years) and 192 (85%) met the WHO criteria for CMML-1. Ninety (40%) patients had SRSF2 mutations (86% CMML-1), 13 (6%) had SF3B1 mutations (75% CMML-1) and 20 (9%) had U2AF35 mutations (95% CMML-1). One-hundred and twenty three (54%) patients had at least one of three spliceosome mutations (86% CMML-1). Mutational hot spots were P95 for SRSF2 (P95L-n=36/H-n=32/R-n=13/A-n=1), K700E (n=7) and H662Q (n=2) for SF3B1, and Q157 (Q157R-n=5/P-n=5/G-n=1) and S34F (n=7) for U2AF35. Seven patients (54%) with SF3B1 mutations had ≥1% RS, with 5 (38%) showing ≥15% RS. Mutations involving all three spliceosome genes were mutually exclusive. The cytogenetic distribution based on the Spanish risk stratification system (Haematologica 2011;96:375) was; SRSF2 mutations: 69 (77%) low risk, 11 (12%) intermediate risk, and 10 (11%) high risk (+8-n=3, del/monosomy 7-n=2, monosomal karyotype-n=5); SF3B1 mutations: 8 (62%) low risk and 5 (38%) intermediate risk; U2AF35 mutations: 15 (75%) low risk, 3 (15%) intermediate risk and 2 (10%) high risk (p=0.89). The distribution of mutations according to the MD Anderson prognostic scoring system [MDAPS] (Blood 2002;99:840) was; SRSF2 - low-n=41, intermediate-1-n=26, intermediate-2-n=18, high-n=5, SF3B1- low-n=7, intermediate-1-n=3, intermediate-2-n=2, high-n=1, and U2AF35- low-n=11, intermediate-1-n=5, intermediate-2-n=3, high-n=1 (p=0.73). There was no statistically significant difference, among the three mutation groups, in prognostically relevant parameters, including gender distribution, median age, hemoglobin values, platelet counts, peripheral blood (PB) and BM blast counts, absolute neutrophil counts (ANC) and absolute monocyte counts (AMC). The only notable difference was that patients with the SF3B1 mutation had a lower median white blood cell count (p=0.04) and a lower absolute lymphocyte count (p=0.045). Results II: Prognostic impact of spliceosome mutations At a median follow-up of 15 months, 166 (73%) deaths and 33 (14.5%) leukemic transformations were documented. Median survivals for patients with mutations involving SRSF2, SF3B1 and U2AF35 were 24, 17 and 12 months, respectively. In univariate analysis, the presence of SRSF2 (p=0.67), SF3B1 (p=0.96) or U2AF35 (p=0.49) mutations had no prognostic impact on OS. Similarly, none of the three spliceosome mutations affected LFS; corresponding p values were 0.55 for SRSF2, 0.9 for SF3B1 and 0.38 for U2AF35 mutations respectively. We then examined possible prognostic value of having none of these mutations (n=104) vs otherwise (n=123) and the results were once again negative (p=0.87). Conclusions: SRSF2 is the most frequently mutated spliceosome gene in CMML, but neither it nor SF3B1 or U2AF35 mutations affect overall or leukemia-free survival in CMML. Furthermore, the current study suggests limited genotype-phenotype association, save for the already established association between SF3B1 mutations and RS. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2803 Background: Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder with overlapping features between myelodysplastic syndromes (MDS) and myeloproliferative neoplasms. Ring sideroblasts (RS) represent abnormal mitochondrial iron accumulation in MDS; with ≥15% RS necessary for the conventional diagnosis of MDS-RS. Somatic spliceosome mutations are recurrent in MDS, with SF3B1 mutations being the most frequent in MDS-RS (∼75%) and SRSF2 in CMML (∼28%). The distribution of these mutations in the presence of both RS and monocytosis is unknown and their prognostic relevance, in the particular setting, undetermined. Methods: Using the Mayo Clinic database for myeloid malignancies (1997–2007), we identified patients who met the 2008 WHO criteria for CMML, and who also displayed at least 1% RS in their bone marrow (BM). All patients underwent BM examination and cytogenetic evaluation at diagnosis and the pathology slides, including iron stains, were centrally re-reviewed to accurately quantify BM RS. DNA was interrogated in the three most frequent spliceosome genes with somatic mutations; SF3B1, SRSF2 and U2AF35. Results: Sixty four patients met the above stipulated criteria for CMML with ≥1% RS; 46 (72%) were males and median age was 71 years (range, 17–90 years). Fifty three (83%) had CMML-1 and the remainder CMML-2. The percentage of patients with ≥15% RS was 41%: 30% had 15–49% RS and 11% had >50% RS. Thirty patients (47%) displayed SRSF2 mutations (mutational frequencies were 58% in the presence of <15% RS, 42% with 15–49% RS and 0% with >50% RS), 9 (14%) SF3B1 mutations (3% with <15% RS, 26% with 15–49% RS and 43% with >50% RS), and 5 (8%) U2AF35 mutations (8% with <15% RS, 11% with 15–49% RS and 0% with >50% RS). Mutational hotspots were P95 for SRSF2 (93%), K700 for SF3B1 (67%) and Q157 for U2AF35 (60%). The three spliceosome mutations were mutually exclusive. At a median follow-up of 26 months, 49 (77%) deaths and 11 (17%) leukemic transformations were documented. In univariate analysis, significant risk factors for survival included increased levels of white blood cell (WBC), absolute neutrophil (ANC), absolute monocyte (AMC), absolute lymphocyte (ALC) counts, the Spanish cytogenetics risk stratification system (Haematologica 2011;96:375), and the presence of circulating blasts. Neither the presence of spliceosome mutations (SF3B1/SRSF2/U2AF35) nor the percentage of RS (considered both as a continuous and a categorical variable), had an impact on either overall or leukemia-free survival. Conclusions: Among spliceosome mutations in CMML, those involving SRSF2 are by far the most frequent, even in the presence of ring sideroblasts. However, in patients with >50% RS, only SF3B1 mutations were seen whereas in those with 15–49% RS, SRSF2 mutations were more common. These observations suggest that SF3B1 mutations play a dominant but not exclusive role in the pathogenesis of RS. Regardless, the current study did not suggest prognostic impact from either the presence of the spliceosome mutations studied or the percentage of RS. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 423 Background: Cytogenetic abnormalities at diagnosis are seen in 20–70% of patients with myelodysplastic syndromes (MDS). The International Prognostic Scoring System -revised (IPSS-R) classifies these cytogenetic abnormalities into five prognostic groups: very good (del(11q), ΠY with overall survival (OS) of 61 months); good (normal, del(20q), del(5q), del(12p) with OS 49 months); intermediate (+8,7q-, i(17q),+19,+21 with OS 26 months); poor (der(3)q21/q26, −7, complex with 3 abnormalities with OS 16 months); and very poor (complex with >3 abnormalities with OS of 6 months) (Schanz J, JCO 2012, Greenberg P, Blood 2012). Monosomal karyotype (MK) is defined as the presence of two or more autosomal monosomies or a single monosomy associated with a structural abnormality. We have previously shown that MK identifies a prognostically worse subgroup of MDS patients with a complex karyotype (Patnaik M, Leukemia 2010). Objectives: Methods: The Mayo Clinic database for MDS was used to identify patients in whom bone marrow histologic and cytogenetic information was obtained at the time of diagnosis. WHO criteria were used for MDS diagnosis and leukemic transformation. Results: i) Patient characteristics: A total of 1,014 patients met the above-stipulated criteria. Median age of the cohort was 71 years (range: 18–98 years) with 684 (67%) males. 819 patients (81%) had primary MDS with 195 cases (19%) of therapy-related MDS. 759 patients (75%) are dead at a median follow-up of 18 months (range: 0–223 months) with leukemic transformation documented in 125 cases (12%). IPSS-R risk distribution was as follows: very low (n=149, 15%), good (n=261, 26%), intermediate (n=221, 22%), high (n=131, 13%), and very high (n=252, 25%). ii) IPSS-R karyotype (Entire cohort; n=1,014): The five cytogenetic groups by IPSS-R were as follows: very good (n=43, 4%), good (n=577, 57%), intermediate (n=187, 18%), poor (n=83, 8%), and very poor (n=124, 12%). We evaluated the prognostic impact of the above groups by Kaplan Meier and Cox proportional hazards analysis. OS for the five cytogenetic groups was as follows: good (36 months), very good (28 months), intermediate (20 months), poor (13 months), and very poor (6 months) (Figure 1). OS of patients with very good karyotype was significantly better than patients with very poor and poor karyotype (p<0.0001, RR 3.2 and p=0.04, RR 1.6 respectively) but similar to patients with intermediate and good karyotype (p=0.22 and 0.28 respectively). iii) IPSS-R karyotype (Primary MDS; n=819): Cytogenetic risk groups by IPSS-R were as follows: very good (n=38, 5%), good (n=512, 63%), intermediate (n=153, 19%), poor (n=46, 6%), and very poor (n=70, 9%). OS of the five groups was as follows: good (39 months), very good (23 months), intermediate (21.5 months), poor (14.5 months), and very poor (6.5 months). OS of patients with very good karyotype was significantly better than patients with very poor karyotype (p=0.0002, RR 2.5) but similar to patients with poor, intermediate and good karyotype (p=0.23, 0.26 and 0.18 respectively). iv) Monosomal karyotype: MK was identified in 153 (15%) cases of which 4 cases were intermediate, 42 poor, and 107 very poor by IPSS-R. OS of patients with MK was similar to those with very poor karyotype (6 months). In addition, OS of patients with very poor without MK was akin to patients with poor without MK (p=0.21). Furthermore, among primary MDS we identified 83 (8%) cases of MK of which 4 were intermediate, 21 were poor, and 58 very poor by IPSS-R. We confirmed that OS of patients with MK was similar to patients with very poor karyotype (6.5 months). Moreover, survival of patients with very poor without MK was similar to patients with poor without MK (p=0.51). Conclusions: In this independent analysis of 1,014 patients with MDS, IPSS-R cytogenetic risk characterization failed to discriminate between very good, good and intermediate prognostic groups. In addition, patients with very poor without MK have a similar prognosis to patients with poor without MK and should be included in the poor category whereas the presence of MK should warrant inclusion into the very poor risk category. Disclosures: No relevant conflicts of interest to declare.