Massive megakaryocyte clustering in triple‐negative primary myelofibrosis associated with an unusual cytogenetic aberration
Abstract Background and purpose: The clinical features and molecular markers of primary myelofibrosis (PMF) in Asian population have rarely been reported. We examined the clinical relevance of molecular markers in a large cohort of PMF patients in Taiwan. Methods: Bone marrow or blood samples at initial diagnosis from 145 patients consecutively diagnosed with PMF based on WHO criteria in Chang Gung Memorial Hospital-Linkou, Taiwan, were examined. EEC assay was performed in a serum free culture system. PRV-1 mRNA expression in granulocytes was measured by real-time RQ-PCR TaqMan assay. Pyrosequencing was used to detect JAK2 V617Fand its allele burden as well as 46/1 rs12343867 genotype in granulocytes. Mutational analysis of MPL (exon 10) was performed by PCR assay followed by direct sequencing. CALR (exon 9) mutations were screened by GeneScan analysis followed by sequencing for those with length changes. Ten of 20 patients progressed to secondary AML (sAML) had matched paired diagnosis and sAML samples available for comparative analysis. Results: Of the 145 patients with PMF, the median age was 64 years, 76 were male, IPSS low risk 25, Int I 23, Int II 41, and high risk 56 patients. In a median follow-up of 35.8 months (range 1.1 to 275.5 months), 20 patients progressed to sAML, 88 patients died with a median overall survival (OS) of 67.4 months. JAK2 V617F was detected in 52% (74/143) patients, CALR mutations in 30% (41/135) (type1 n=29; type 2 n=5; and others n=7), MPL mutations in 4% (5/141) (n=2/2/1 for W515L/K/A), and 11.0% of PMF patients were triple-negative. The incidence of 46/1 haplotype in 112 patients analyzed was TT 32 %, CT 36 %, and CC 32 %; C-allele frequency was significantly higher in PMF compared with 50 normal subjects (50% vs. 24%; P< 0.0001).EEC growth was detected in 48.9% (45/92) of patients examined. PRV-1 over-expression was present in 40% (28/70) of patients. Of the 10 matched paired PMF/sAML samples, 6 patients had CALR mutations with similar allele burden at both phases of disease whereas sAML evolved from a non-JAK2 V617F clone in one of the 3 patients carrying JAK2 V617F at diagnosis. Patients with EEC growth or PRV-1 over-expression were significantly associated with younger age, higher WBC and platelet counts. EEC-positive patients had higher Hb level and lower circulating blasts. JAK2 V617F was closely associated with higher WBC and platelet counts whereas patients with CALR mutations had lower WBC counts. None of these molecular markers had a correlation with constitutional symptom, IPSS, occurrence of thrombosis or risk of sAML transformation. EEC growth conferred a favorable leukemia-free survival (LFS) (P =0.019) and OS (P =0.013) compared with those without EEC. PRV-1 over-expression was associated with better OS (P =0.036). JAK2 V617F and MPL mutations did not influence LFS and OS. Allele burden of JAK2 V617F had no impact on outcomes. CALR mutations were associated with a favorable OS compared with mutation-negative patients (P =0.034). There were no difference in outcomes between type 1 and type 2 mutations of CALR. Patients with triple-negative mutations had a significantly inferior OS (P =0.020). CT genotype (46/1) was associated with shorter LFS (P =0.026). EEC growth was strongly associated with PRV-1 over-expression and JAK2 V617F mutation, whereas EEC formation and CALR mutations were mutually exclusive. In multivariate analysis, EEC growth was the most important predictor for LFS (HR 0.058; 95% CI: 0.005-0.676, P =0.023) and OS (HR 0.21; 95% CI 0.076-0.581, P =0.003) among the molecular markers; CALR mutations also held favorable OS (HR 0.245; 95% CI 0.085-0.709, P =0.009). Conclusions: Approximately 90% of PMF patients in Taiwan had JAK2 V617F, CALR, or MPL mutations, half were associated with C-allele genotype, 78% had EEC growth and /or PRV-1 over-expression. EEC growth was the most important independent factor for predicting better outcomes and CALR mutations also conferred a favorable OS. (Grant support: NSC96-2314-B-182-003, CMRPG330303, OMRPG3C0021, and MOHW103-TD-B-111-09) Disclosures No relevant conflicts of interest to declare.
Background Myeloproliferative neoplasms (MPNs) are chronic hematopoietic stem cell disorders, including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (MF). JAK2, MPL, and CALR mutations are considered as "driver mutations" and are directly implicated in the disease pathogenesis by activation of JAK/STAT signaling. However, some patients do not harbor any of these mutations. Since such triple-negative MPNs are very rare, no specific molecular markers were established to use for a precise differential diagnosis yet. So far, the introduction of next generation sequencing (NGS) technologies in research of myeloid neoplasms has provided valuable contributions on the identification of new molecular biomarkers, establishing more accurate risk rating and selection of more specific therapeutic interventions. This study aimed to identify, through targeted deep sequencing, specific genetic variants in patients with triple-negative MPNs. Methods We performed NGS targeted sequencing in 18 Brazilian triple-negative patients (11 MF and 7 ET). The median age at diagnosis was 64 years for primary myelofibrosis (range 42-78), and 52 years for essential thrombocythemia (range 19-79). In 14 cases, we used the Illumina TruSight Myeloid Panel covering 54 genes and in 4 cases we used a custom Sure Select Agilent panel containing more than 300 genes previously reported to be related to myeloid neoplasm. The inclusion criteria for variant filtering was quality score>30, read count>50, minor allele frequency<0.05, frameshift, nonsense, splice site and 5`UTR variants, and missense variants described as deleterious for at least three prediction softwares. Results Possible pathogenic mutations were identified in 33 genes by Illumina and/or Agilent panels. Frameshift/nonsense or missense variants previously described as pathogenic correspond to 11 variants (Table 1). Out of these, mutations in TET2 were the most frequently identified (in 9/18 (50%) of the cases). In three MF patients with TET2 mutations no other considered pathogenic mutation was identified, indicating a possible role of TET2 as a driver gene. According to previous reports, the frequency of TET2 mutations in triple-negative MPNs patients were only 7%. Phenotypically, in our triple-negative MPNs, 6/11 (54.5%) MF and 3/7 (42.9%) ET patients harbored TET2 mutations. Clinically, the adverse prognostic impact of TET2 mutations in MPN had not been consistently shown by previous studies. In addition, mutations in SF3B1, CEBPA, and KMT2A genes were the second most frequent ones detected in 2/18 each (11%) of the patients, some of which were concomitant with TET2 mutations, suggesting additional clonal advantage due to these genetic events. Other potentially pathogenic variants were also detected is genes that have been reported to be related to other myeloid neoplasms (KMT2A, CDKN2A, TERT, DIS3, ZFPM1, PCDHA8, SAMD9, SAMD9L, DCLRE1C,ERBB3, SDHA, PCDHA6, SVEP1, MAP2K1 and EP300). Conclusions We have characterized the genomic alterations in 18 Brazilian patients with MPN triple-negative for either JAK2, CALR or MPL main mutations. Using a sensitive NGS platform, we identified significantly more frequent mutations in TET2 gene (in as many as a half of the cases) compared to JAK2, MPL, CALR mutation-positive MPN cases. We also uncovered mutations in genes not previously related with in MPN. Our novel findings call for further studies validating the frequencies, biological significance, and prognostic impacts of somatic mutations in triple-negative MPNs. Disclosures Ogawa: Qiagen Corporation: Patents & Royalties; RegCell Corporation: Equity Ownership; Kan Research Laboratory, Inc.: Consultancy; Asahi Genomics: Equity Ownership; ChordiaTherapeutics, Inc.: Consultancy, Equity Ownership; Dainippon-Sumitomo Pharmaceutical, Inc.: Research Funding.
Abstract Introduction: Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF) are myeloproliferative neoplasms (MPN) with similar driver mutations. The three hallmark molecular alterations in these diseases are JAK2, MPL and CALR mutations. Patients with myelodysplastic/myeloproliferative (MPN/ MDS) neoplasms such as refractory anemia with ring sideroblasts and thrombocytosis (RARS-T) also present with the same hallmark genetic changes. Nevertheless, roughly 10% of these patients do not present mutations in neither of these genes. Recent data suggest that triple negative patients have a more aggressive clinical course. While the molecular alterations present in patients with MPN have been extensively studies, the genomic profile of triple negative TE/PMF/RARS-T has not been described. To better characterize these patients we performed whole exome / genome sequencing of paired granulocytes and skin from 15 triple negative MPN patients Methods: A total of 15 patients with triple negative MPN or MPN/ MDS [PMF (N=6)/TE (N=8)/RARS-T (N=1)] were analyzed. DNA was extracted from CD66b+ magnetic bead selected granulocytes (EasySep, Stem Cell Technologies) and matched skin biopsies with QiaAmp DNA Mini kit (Qiagen). Whole-exome targeted capture was carried out on 3 μg of genomic DNA, using the SureSelect Human Exome Kit 51Mb version 4 (Agilent Technologies, Inc., Santa Clara, CA, USA). The exome library was sequenced with 100 bp paired-end reads on an Illumina HiSeq2000. Somatic variants calls were generated by combining the output of Somatic Sniper (Washington University), Mutect (Broad Institute) and Pindel (Washington University). Tumor coverage was 150x and germline coverage was 60x. The combined output of these 3 softwares was further filtered by in-house criteria in order to reduce false-positive calls (minimum coverage at both tumor/germline ≥8 reads; fraction of reads supporting alternate allele ≥5% in tumor and ≤10% in germline; ratio of allele fraction tumor:germline >2). All JAK2 and CALR mutations were validated through Sanger sequencing. Validations of other somatic mutations are under way at this point. Results: First we asked whether other hematopoietic related genes could be responsible for the pathogenesis of the triple negative cases. With that goal we searched for high confidence mutations in genes that are mutated in at least 1% of patients with hematopoietic tumors on COSMIC (catalog of somatic mutations in cancer) database and also genes known to be recurrently mutated in myeloid malignancies. Only 6 out of 15 patients presented mutations in other myeloid related genes. The diagnosis of these patients were PMF=4, TE=2. The hematopoietic related genes mutated in these patients were: ASXL1 (n=4), CUX1 (n=3), NRAS (n=2) and ATM, CBL, CSFR3, CREBBP, DNMT3A, ETV6, EZH2, JARID2, MLL2, PHF6, SRSF2, STAG2, TET2, GNAS, U2AF1 (n=1). Noteworthy, we have found one known oncogenic mutation in CSFR3, an alteration supposed to be specific for chronic neutrophilic leukemia and atypical CML, in a patient with ET, and an oncogenic mutation in GNAS in a patient with PMF. In addition, the patient with RSRA-T had a putative oncogenic mutation in PTPN11 Remarkably, the average number of hematopoietic related mutations in these patients was 5, significantly higher than the total number of mutations found in another cohort of patients with either JAK2 (average = 1.7) or CALR mutations (average = 1.9). Although our numbers are small, we may speculate that the high incidence of ASXL1 mutations (28%) associated with a high number of prognostically detrimental mutations can partially explain the worse outcomes associated with triple negative MPN. Noteworthy is also the high prevalence of CUX1 mutations in this subset of patients (21%) when compared to other myeloid malignancies in general. Regarding the other 9 patients for whom no hematopoietic mutations could be identified, 6 patients had ET, 2 patients PMF and one patient had RARS-T. Conclusion: We have shown that: i-patients with triple negative MPN are molecularly heterogeneous, with one group presenting a high number of hematopoietic related mutations, ii-the most common mutations present in these patients are ASXL1, CUX1 and NRAS, iii-The majority of these patients do not present mutations in hematopoietic related genes, what suggests that non-described molecular mechanisms are operating in these patients. Disclosures No relevant conflicts of interest to declare.
AimsWe investigated the clinical and prognostic relevance of the mutational status of driver genes with allele burden and endogenous erythroid colony (EEC) growth in 203 Taiwanese patients with primary myelofibrosis (PMF).MethodsPyrosequencing was used to detect JAK2V617F mutational status and measure allele burden, while MPL (exon 10) mutations were analysed by PCR assay and then by direct sequencing. CALR exon 9 mutations were first screened for length changes by GeneScan followed by sequencing. The allele burden of the mutated CALR gene was measured by pyrosequencing. The EEC assay was conducted using a serum-free culture system.ResultsThe frequencies of the three driver mutations and triple-negative status were similarly distributed between pre-PMF and overt PMF patients, except that pre-PMF patients had a higher incidence of CALR type 2/type-2 like mutations and a lower JAK2V617F allele burden. EEC growth and CALR mutations conferred favourable overall survival (OS). A lower JAK2V617F allele burden and grade 3 bone marrow fibrosis were associated with shorter OS and decreased leukaemia-free survival (LFS). Type 2/type 2-like CAL mutations were associated with better LFS compared with type1/type 1-like mutations. Patients with triple-negative mutation status had significantly worse OS and LFS. The allele burden of CALR mutations remained unchanged, while some JAK2V617F mutations showed clonal expansion in patients during secondary acute myeloid leukaemia transformation.ConclusionsOur study showed that EEC growth, a higher JAK2V617F allele burden and CALR mutations, especially type 2, were independent predictors for better outcomes in PMF. The allele burden of CALR mutations remained stable, but the allele burden of JAK2V617Fmutations was variable during leukaemia transformation.
The aim of the present paper was to evaluate the clinical features and risk of thrombotic events (TE) in patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF), depending on the molecular characteristics of disease. Clinical data and laboratory parameters were analyzed in 50 ET patients and 50 PMF ones who had been followed up at the Department for Standardization of Treatments, National Research Center for Hematology, Ministry of Health of the Russian Federation, from February 2015 to September 2016. The patients with ET and those with PMF were found to have a high risk of TE. The risk for TE in the patients with ET is higher (24% in the entire group) than in those with PMF (14% in the study group). In ET, there is a high thrombosis risk in the detection of JAK2 and CALR gene mutations as compared with triple-negative cases. The PMF patients with JAK2 V617F mutations are at high risk for TE compared to those who are CALR mutation carriers and in triple-negative cases. There was no significant association of TE with high thrombocytosis. A factor, such as age, was found to be of no negative prognostic value in the patients with PMF.
Lack of demonstrable mutations affecting JAK2, CALR, or MPL driver genes within the spectrum of BCR-ABL1-negative myeloproliferative neoplasms (MPNs) is currently referred to as a triple-negative genotype, which is found in about 10% of patients with essential thrombocythemia (ET) and 5–10% of those with primary myelofibrosis (PMF). Very few papers are presently available on triple-negative ET, which is basically described as an indolent disease, differently from triple-negative PMF, which is an aggressive myeloid neoplasm, with a significantly higher risk of leukemic evolution. The aim of the present study was to evaluate the bone marrow morphology and the clinical-laboratory parameters of triple-negative ET patients, as well as to determine their molecular profile using next-generation sequencing (NGS) to identify any potential clonal biomarkers. We evaluated a single-center series of 40 triple-negative ET patients, diagnosed according to the 2017 WHO classification criteria and regularly followed up at the Hematology Unit of our Institution, between January 1983 and January 2019. In all patients, NGS was performed using the Illumina Ampliseq Myeloid Panel; morphological and immunohistochemical features of the bone marrow trephine biopsies were also thoroughly reviewed. Nucleotide variants were detected in 35 out of 40 patients. In detail, 29 subjects harbored one or two variants and six cases showed three or more concomitant nucleotide changes. The most frequent sequence variants involved the TET2 gene (55.0%), followed by KIT (27.5%). Histologically, most of the cases displayed a classical ET morphology. Interestingly, prevalent megakaryocytes morphology was more frequently polymorphic with a mixture of giant megakaryocytes with hyperlobulated nuclei, normal and small sized maturing elements, and naked nuclei. Finally, in five cases a mild degree of reticulin fibrosis (MF-1) was evident together with an increase in the micro-vessel density. By means of NGS we were able to identify nucleotide variants in most cases, thus we suggest that a sizeable proportion of triple-negative ET patients do have a clonal disease. In analogy with driver genes-mutated MPNs, these observations may prevent issues arising concerning triple-negative ET treatment, especially when a cytoreductive therapy may be warranted.
Abstract Introduction Young adults with Essential Thrombocythemia (ET) or early Primary Myelofibrosis (early-PMF) are a category of patients projected to a prolonged survival but also to an extended utilization of medical resources. Mutations, including those in the calreticulin (CALR) gene, have been reported to affect main clinical features and outcome in large cohorts of patients with Ph-negative MPNs. However, no data are available on mutational status and long-term outcome in young MPN patients. Methods A clinic-pathologic database of ET patients followed in 5 Italian Hematology Centers was created. A total of 217 WHO-diagnosed ET or early-PMF patients ≤ 40 years at diagnosis was retrieved from the general database of 2635 patients. All bone marrow biopsies were reviewed at local institution. Baseline clinical/molecular characteristics and outcome measures (thrombosis, hemorrhages, secondary MF and AL, second neoplasia, death, overall and event-free survival) were evaluated. JAK2V617F allele-burden was assessed in granulocyte DNA by using ipsogen JAK2 MutaQuant Kit (qPCR). CALR mutations were identified by next generation sequencing (NGS) approach on GS Junior (Roche-454 platform); MPL mutations were evaluated by using ipsogen MPLW515L/K MutaScreen Kit. Results Overall, 197 WHO-defined ET and 20 early-PMF (age range: 16-40, median 34) were included in the study. Mutational frequencies were 61% for JAK2, 25% for CALR, 1% for MPL and 13% for triple negative. Baseline clinical characteristics and use of antiplatelet/cytoreductive therapies were comparable in ET and early-PMF, although frequency of triple negative was higher in the early-PMF cohort. Compared to the JAK2 positive population, both CALR and triple-negative patients showed higher platelet count and lower hemoglobin and hematocrit levels (Table 1). Median follow-up was 10.2 years (range: 0.5-37.5). During follow-up, 19 (9,6%) ET and 3 (15%) early-PMF patients experienced a total of 31 thrombotic (arterial: 38%) and 12 hemorrhagic events, with an incidence rate of 0.91% and 0.39% patients/yr, respectively. The cumulative incidence of thrombosis was 0,14% and 0,24% at 15 and at 20 years, respectively. Overall, 10 patients (4,6%) and 1 (0,4%) patients evolved to MF and AL, respectively; 10 developed a second neoplasia. The cumulative incidence of disease progression into MF/AL was 0,03% and 0,13% at 15 and at 20 years, respectively. At last contact, 6 (2,7%) patients had died, at a median age of 61 years (20-71), for an overall survival of 98% at 15 years. Causes of death were related to the myeloproliferative neoplasm (disease evolution or thrombotic complications) in all patients but one. Event-free survival was similar in the ET/early-PMF cohorts considering both every event separately and all together. In univariate analysis, male sex (p=0.003), previous thrombosis (p=0.001), splenomegaly (p=0.037), JAK2V617F (p=0.019) were associated with increased thrombotic risk; in multivariate Cox analysis, only previous thrombosis and male sex remained significant (p=0.012). Baseline splenomegaly was the only predictive factor for subsequent hemorrhages (p=0.017). Abnormal karyotype was associated with secondary MF (p=0.013) and also with second neoplasia (p<0.001). Together with JAK2V617F positivity and leukocytosis >11x109/L, abnormal karyotype was also associated with worse survival in univariate analysis. However, in multivariate analysis only JAK2V617F mutation remained as negative predictor of survival (p=0.019). Also, multivariable analysis confirmed JAK2 mutation and splenomegaly as independent risk factors for cumulative events. Conclusions With the limitations due to the low number of early-PMF, the outcome of young adults with early-PMF and true ET seemed to be comparable. The correlation of abnormal karyotype with MF transformation and second neoplasia suggests the need for an accurate cytogenetic analysis at diagnosis. Mutational status did influence disease phenotype, in terms of baseline characteristics and prognosis. Indeed, JAK2 mutational status confirmed a negative prognostic role for thrombosis and survival, while event-free survival was significantly better in triple-negative patients. Notably, causes of death were mostly related to the hematological malignancy, pointing out the substantial impact that this generally indolent disease may acquire in young adults. Disclosures Latagliata: Novartis: Consultancy; Bristol Myers-Squibb: Consultancy; Celgene: Consultancy; Shire: Consultancy. Cavo:Janssen: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; BMS: Consultancy, Honoraria; Millenium: Consultancy, Honoraria; Onyx: Honoraria.
Abstract Background: We have long introduced the concept of host genetic variations in the phenotypic diversity of myeloproliferative neoplasms (MPN) (Blood 2008;111:2785). Previous studies have established an association between JAK2 mutations in myeloproliferative neoplasms (MPN) and the germline GGCC (46/1) haplotype, which constitutes a string of single nucleotide polymorphisms (SNPs) near the JAK2 gene that are inherited together on chromosome 9p (reviewed recently;Int J Mol Sci. 2018; 19: 1152). In 2010, we reported an association between shortened survival in primary myelofibrosis (PMF) and nullizygosity for the JAK2 46/1 haplotype (Leukemia 2010; 24:105), although our findings were not confirmed in another study (Leukemia 2010; 24:1533). Others have reported an association with splanchnic vein thrombosis, that was not accounted for by JAK2 mutations (Ann Hematol 2014;93:1845). In the current study, we have increased the number of informative cases to 414 (from 130 reported in 2010), in order to revisit with the phenotypic and prognostic relevance of the JAK2 46/1 haplotype in PMF. Methods : Study patients were recruited from the Mayo Clinic, Rochester, MN, USA. Diagnoses PMF and its leukemic transformation were confirmed by both clinical and bone marrow examinations, in line with the 2016 World Health Organization criteria (Blood. 2016;127:2391). Screening for the JAK2 46/1 haplotype included rs12343867 SNP genotyping, as previously detailed (Leukemia 2010; 24:105), and using a commercially available TaqMan SNP genotyping assay (Applied Biosystems Inc., Foster City, CA, USA). Statistical analyses considered clinical and laboratory data collected at the time of initial PMF diagnosis or Mayo Clinic referral point. Conventional statistics was used for confirming phenotypic associations and calculation of overall (OS) and leukemia-free (LFS) survival. The JMP® Pro 13.0.0 software from SAS Institute, Cary, NC, USA, was used for all calculations. Results: 414 patients with PMF (median age 63 years; 63% males) were included in the current study; among 324 evaluable cases, MIPSS70+ version 2.0 risk distribution was 18% very high risk, 41% high risk, 19% intermediate risk, 18% low risk and 4% very low risk. Driver mutation distribution was 63% JAK2, 17% type 1-like CALR, 3% type 2-like CALR, 7% MPL and 10% triple-negative. JAK2 46/1 haplotype was documented in 69% of the study patients, including 25% in homozygous and 44% in heterozygous state. Driver mutation frequency in patients homozygous/heterozygous/nullizygous for the 46/1 haplotype was 78%/60%/56% JAK2, 10%/20%/18% type 1-like CALR, 3%/2%/5% type 2-like CALR, 4%/8%/7% MPL and 6%/10%/14% triple-negative (p=0.02). The three 46/1 haplotype groups were phenotypically mostly similar, with the exception of platelet count (p=0.02) and leukocyte count (p=0.003), which were both higher with homozygous 46/1 haplotype. In univariate analysis, nullizygosity for the JAK2 46/1 haplotype was associated with inferior overall survival (HR 1.5, 95% CI 1.1-1.9; figure 1a); this survival effect was most pronounced in JAK2 mutated cases (figure 1b; p<0.001), as opposed to CALR/MPL mutated cases (figure 1c; p=0.48) or triple-negative cases (figure 1d; p=0.27). Multivariable analysis that included age and other genetic risk factors, including karyotype, driver mutational status and presence of high molecular risk mutations, such as ASXL1 and SRSF2, confirmed the independent prognostic contribution of nullizygosity for the 46/1 haplotype (p=0.02; HR 1.4, 95% CI 1.1-1.8). Nullizygosity for 46/1 also remained significant in the context of the recently unveiled genetics-based prognostic model, GIPSS (genetically-inspired prognostic scoring system) (p=0.04) (Leukemia.2018 doi: 10.1038/s41375-018-0107-z), but not in the context of MIPSS70+ version 2.0 (karyotype and mutation-enhanced international prognostic scoring system for transplant-age patients) (p=0.4). (JClinOncol.2018 doi: 10.1200/JCO.2018.78.9867). Leukemia-free survival was not affected by the 46/1 haplotype (p=0.6). Conclusions: The current study confirms the association of nullizygosity for the JAK2 GGCC (46/1) haplotype with inferior survival in PMF, primarily in JAK2-mutated cases; the observed survival effect was independent of currently acknowledged genetic risk factors, including karyotype and high molecular risk mutations. Disclosures No relevant conflicts of interest to declare.
Abstract Background Patients with primary myelofibrosis survive for a median of 5-7 years after diagnosis. However, survival outcomes markedly vary; some patients experience rapid progression and others survive for 10 years or more. The international prognostic scoring system (IPSS) stratifies patients into 4 risk groups on the basis of clinical features (age and constitutional symptoms) and blood counts (hemoglobin, white blood cells, and the presence of circulating blasts). Most patients with primary myelofibrosis harbor mutually exclusive somatic mutations in 1 of 3 genes. In 60% of patients, a substitution mutation is detected in the Janus Kinase 2 (JAK2) gene (JAK2V617F). In another 30% of patients, a frameshift mutation is identified in the Calreticulin (CALR) gene. In 5% of patients, a substitution mutation is found in the gene that codes for the thrombopoietin receptor (MPL). Although patients with mutated CALR generally have more indolent disease than patients with JAK2V617F, the prognostic significance of harboring JAK2V617F is confounded by the observation that low JAK2V617F allele burden is associated with aggressive disease and shortened overall survival (OS) duration. Aim To develop a prognostic model based on the mutation status of the JAK2, CALR, and MPL genes and to determine whether JAK2, CALR, and MPLmutation status provides additional prognostic value to the IPSS. Patients and methods Bone marrow samples were collected and processed from 344 patients with primary myelofibrosis at The University of Texas MD Anderson Cancer Center between 2000 and 2013 (157 months), at the initial visit. All samples were screened for JAK2V617F and for exon9 deletion or insertion mutations in CALR. We used quantitative PCR to quantify the levels of wild-type and mutated JAK2 and determine the JAK2V617F burden. Patients who did not have a mutation in either gene (n = 73) were also screened for an exon10 substitution mutation in MPL. Results Of the 344 patients screened for JAK2V617F and mutations in CALR, 226 (66%) had JAK2V617F and 43 (13%) had mutations in CALR. Of the 75 patients who did not have JAK2 or CALR mutations, 16 (21%) had mutated MPL. In 59 patients (17%), we did not identify mutations in any of the genes (“triple negative”). In the 226 patients who harbored the JAK2V617F mutation, a cut-point of 50% dichotomized patients into those with a high JAK2V617F burden (≥50%) and a favorable survival outcome (median OS: 80 months, 95% confidence interval [CI]: 51-109 months) and those with a low JAK2V617F burden and an adverse survival outcome (median OS: 50 months, 95% CI: 40-60 months; Figure 1). Clinically, patients with a high JAK2V617F burden had larger spleens than those with a low JAK2V617Fburden (P < .0001). We then classified patients according to mutation status into 5 groups: mutated CALR, mutated MPL, high JAK2V617F burden, low JAK2V617F burden, or triple negative) and used mutation status and the IPSS to fit a multivariate model to predict OS. In this model, the IPSS and mutation status independently predicted OS, and as implicated by the higher p-value of the Wald chi-square test, the mutation status was a superior estimate of OS. On the basis of this analysis, patients were stratified according to mutation status into 3 groups with different survival outcomes. Patients had a favorable outcome if they harbored CALR or MPL mutations or if they had a high JAK2V617F burden (n = 170, OS: 104 months, 95% CI: 86-122 months). Patients who were triple negative had an intermediate survival outcome (n = 59, OS: 56 months, 95% CI: 35-77 months). Patients with a low JAK2V617F burden had an adverse outcome (n = 115, OS: 45 months, 95% CI: 38-52 months; Figure 2). The risk of transformation to acute myeloid leukemia was similar across groups except that patients with a low JAK2V617Fburden had a lower risk of transformation (hazard ratio = 0.27, 95% CI: 0.1-0.8). Conclusion On the basis of mutation status in JAK2, CALR, and MPL, we stratified patients into 3 groups with good (CALR or MPL mutation or high JAK2V617F burden), intermediate (triple negative), or adverse (low JAK2V617Fburden) survival outcomes. Our results indicate that prognostication based on mutation status is independent of and superior to the IPSS. Figure 1: Overall survival in patients with primary myelofibrosis with a high or low JAK2V617Fburden Figure 1:. Overall survival in patients with primary myelofibrosis with a high or low JAK2V617Fburden Figure 2: Overall survival in patients with primary myelofibrosis, stratified by mutation status into 3 risk groups Figure 2:. Overall survival in patients with primary myelofibrosis, stratified by mutation status into 3 risk groups Disclosures No relevant conflicts of interest to declare.
Myelofibrosis (MF) can occur due to a wide variety of causes including malignant lymphoma. We report a case of splenic marginal zone lymphoma complicated by MF mimicking primary myelofibrosis (PMF). The JAK2, CALR and MPL mutations are detected in more than 90% of PMF cases, and when detected, the diagnosis of PMF is usually straight forward. Mutational analysis should be done in all cases of MF, and in triple-negative cases, an exhaustive investigation of other causes of MF should be carried out before a diagnosis of triple-negative PMF is rendered.
