Essential Thrombocythemia in Children and Adolescents

This paper reviews the features of pediatric essential thrombocythemia (ET). ET is a rare disease in children, challenging pediatric and adult hematologists alike. The current WHO classification acknowledges classical Philadelphia-negative MPNs and defines diagnostic criteria, mainly encompassing adult cases. The presence of one of three driver mutations (JAK2V617F, CALR, and MPL mutations) represent the proof of clonality typical of ET. Pediatric ET cases are thus usually confronted by adult approaches. These can fit only some patients, because only 25–40% of cases present one of the driver mutations. The diagnosis of hereditary, familial thrombocytosis and the exclusion of reactive/secondary thrombocytosis must be part of the diagnostic process in children and can clarify most of the negative cases. Still, many children present a clinical, histological picture of ET, with a molecular triple wild-type status. Moreover, prognosis seems more benign, at least within the first few decades of follow-up. Thrombotic events are rare, and only minor hemorrhages are ordinarily observed. As per the management, the need to control symptoms must be balanced with the collateral effects of lifelong drug therapy. We conclude that these differences concert a compelling case for a very careful therapeutic approach and advocate for the importance of further cooperative studies.

Download Full-text

Primary Trombocythemia in Children and Adolescents Includes Different Subtypes Compared to Adult Essential Thrombocythemia

Blood ◽

10.1182/blood.v124.21.1865.1865 ◽

2014 ◽

Vol 124 (21) ◽

pp. 1865-1865

Author(s):

Fiorina Giona ◽

Marica Laurino ◽

Luciana Teofili ◽

Sara Capodimonti ◽

Maurizio Martini ◽

...

Keyword(s):

Children And Adolescents ◽

Essential Thrombocythemia ◽

Conflicts Of Interest ◽

Correct Diagnosis ◽

Young Patients ◽

Antiplatelet Agents ◽

Wild Type ◽

Primary Thrombocythemia ◽

Calr Mutations

Abstract The recent discovery of various mutations of the CALR gene that are mutually exclusive with JAK2 and MPL mutations has allowed a correct diagnosis in about 90% of adult cases of essential thrombocythemia (ET). Moreover, the mutation status of JAK2 and CARL defines subtypes of ET in adults with a substantially different clinical course and outcome. Based on our experience, we suggested that primary thrombocythemia (PT) in children is characterized by subtypes that differ from those found in adult ET. The present study was carried out in children and adolescents with PT in order to (a) characterize the various subtypes of the disease and (b) analyze their clinical and biologic features, treatment approach and outcome. PT patients aged <20 years (yrs) at diagnosis (dx) were evaluated for mutations of JAK2, thrombopoietin (TPO) and its receptor (MPL) and CALR genes, and for clonal hematopoiesis (females). The presence of MPLS505A (confirmed on DNA from buccal swabs) defined a hereditary thrombocytosis (HT). ET was diagnosed according to WHO 2008 criteria. For wild type patients, an additional inclusion criteria was a follow-up >24 months. Among 58 PT patients (males: 23; females: 35; median age at dx: 14.4 yrs), 21 (36%) had HT due to MPLS505A, 14 were JAK2V617F-mutated (24%), 9 (16%) harbored CALR mutations and 14 (24%) were wild type for JAK2, CALR and MPL (Fig 1). JAK2- and CALR-mutated were older than those with wild type ET or with HT (median age, 17.6 and 16.1 vs 10.4 and 13.7 yrs, p .028). As to the hematologic findings, HT patients showed both hematocrit values (median, 36.3%) and leukocytes counts (median, 9.53 x109/L) significantly lower than ET patients, whatever the subtypes (median, 41.2% and 11.2 x109/L, p .006 and p .029, respectively). No differences were found with regard to platelets both between HT and ET and among the different ET subtypes. JAK2-mutated patients exhibited more frequently symptoms (69%) compared to CALR-mutated (22%), wild-type ET (14%) and HT (14%) patients (p. 0057). Splenomegaly at diagnosis was recorded more frequently in JAK2-mutated than in CALR-mutated or wild type-ET or HT (50%, 33% 21% and 14% , respectively, p .122). Antiplatelet agents, mostly acetylsalicylic acid (ASA), were started less frequently in HT than in ET patients, irrespective of the subtypes (57% vs 81%, p .05). The use of ASA progressively decreased over the time; at the last follow-up, 2 patients with HT, 2 CALR-mutated and 1 JAK2-mutated patients were still receiving ASA, while no wild type ET patient was on treatment. Cytoreductive agents, hydroxyurea and/or interferon and/or anagrelide, were used in a minority of HT patients (19%) in comparison with ET patients (65%), p .001, mainly with those wild-type (78%, p <.001). At the last observation, one HT patient was still receiving cytoreductive agents compared to 30% of ET patients whatever the subtypes (p .024). After a median follow-up of 196 months (similar in the different subtypes), all patients are alive. On the whole, 5 thrombotic events were recorded in 3 patients with HT and in 2 ET patients (1 JAK2-mutated and 1 JAK2 and CALR wild-type), without any significant thrombophilic abnormalities during treatment with ASA and/or cytoreductive agents. A progressive splenomegaly was recorded in 9 (15%) patients (2 HT, 4 JAK2-mutated, 3 CALR-mutated) and it was combined with grade ≥2 medullar fibrosis in 2/4 JAK2-mutated and in 2/3 CALR-mutated patients. None of the JAK2 and CALR wild-type patients had spleen enlargement or reticulin fibrosis (p .022). Two untreated patients (1 HT and JAK2 and CALR wild-type) developed malignancies. On the whole, these data emphasize that in young patients with PT, hereditary forms can be frequently observed. Thrombotic events, recorded mainly in HT patients despite treatment with ASA, were probably due to a MRP4 protein overexpression that was found in our MPLS505A HT. Moreover, our observations highlight that, in contrast to adult ET, more than one third of young ET patients have no JAK2 or CALR mutations. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Download Full-text

Cytoreductive Therapeutic Approach in the Essential Thrombocythemia (ET) Patients of the Registro Italiano Trombocitemia (RIT): Preliminary Data

Blood ◽

10.1182/blood.v112.11.5248.5248 ◽

2008 ◽

Vol 112 (11) ◽

pp. 5248-5248

Author(s):

Luigi Gugliotta ◽

Alessia Tieghi ◽

Anna Candoni ◽

Monia Lunghi ◽

Gianluca Gaidano ◽

...

Keyword(s):

Bone Marrow ◽

Essential Thrombocythemia ◽

Therapeutic Approach ◽

Jak2 V617f ◽

Bone Marrow Biopsies ◽

Thrombotic Risk ◽

Significant Difference ◽

Cytoreductive Treatment ◽

Wbc Count

Abstract Background: the Registro Italiano Trombocitemia, that is a GIMEMA project, has been activated to registry Italian Essential Thrombocythemia (ET) patients, to improve the diagnosis appropriateness (WHO criteria), to verify the prognostic value of the clinical and biological parameters, to evaluate the compliance to the therapeutical Italian guidelines (1), and to create a network for activation of new studies. Objective: this analysis is mainly devoted to describe the ET patients registered in the RIT and to evaluate the therapeutic approach adopted in the 102 participating hematological centers. Material and methods: two thousand and fifteen ET patients have been registered after the written informed consent was obtained, and data validation by various expert panels is in progress. This preliminary report considers 1785 patients, diagnosed mainly (1078, 60.4%) since the publication in the year 2004 of the ET therapy Italian guidelines (1). Results: the patients, 678 (38%) males and 1107 (62%) females, showed at diagnosis: age 60.3 ± 16.8 years with higher values in males than in females (61.7 ± 15.3 vs. 59.4 ± 17.7, p<0.05), being the patients below 40 years 14% and those over 70 years 33% of cases; PLT count (109/L) 846 ± 309 with lower values in males than in females (813 ± 261 vs. 866 ± 334, p<0.002), and with values 1001–1500 and over 1500 in 16% and 4% of cases, respectively; WBC count (109/L) 9.1 ± 2.9, without difference by sex, and with values 12–15 in 10% and over 15 in 3% of cases; Hgb (g/dL) 14.2 ± 1.6 with higher values in males than in females (14.8 ± 1.5 vs. 13.8 ± 1.5, p<0.001), and with values over 16.5 in 8.5% of males and 2.7% of females, respectively; splenomegaly in 488 (27%), echo-documented in 324 cases (18%); history of hemorrhage and thrombosis in 90 (5%) and 325 (19%) of cases, respectively; disease-related symptoms in 41% and general thrombotic risk factors in 93% of cases, respectively. The WHO 2001 diagnostic criteria were reported for 33% of cases observed before the year 2004 and for 53 % of cases observed since the year 2004. Detailed data at diagnosis were reported as follows: bone marrow biopsy in 1087 cases (61%) with a frequency of 51% and 68% before and since the year 2004, respectively; bcr-abl study in 1045 cases (59%); cytogenetics in 828 cases (46%) with karyotype abnormalities in 27 patients (3%). The JAK2 V617F mutation, searched in 574 cases (32%), was observed in 320 of them (56%). The patient follow-up was 4.5 ± 4.5 years with a total of 5245 pt-yrs. During the follow-up the hemorrhagic events were 5.7% (1.3/100 pt-yrs), being the major events 1.9% (0.4/100 pt-yrs); the thrombotic complications were 14.9 % (3.3/100 pt-yrs), resulting the major arterial 9.4% (2.1/100 pt-yrs), the major venous 3.5% (0.8/100 pt-yrs) and the minor thrombosis 2% (0.4/100 pt-yrs). An antiplatelet treatment, almost always with low dose aspirin, was performed in 75% of the patients, without significant difference in the cases diagnosed before and since the 2004. A cytoreductive treatment was done with use of Hydroxyurea (HU, 64%), Interferon alpha (IFN, 16%), Anagrelide (ANA, 15%), Busulfan (BUS, 4%), and Pipobroman (PIPO, 2 %). In the ET patients diagnosed since the year 2004 respect those diagnosed before, it was observed a decrease in the use of all the cytoreductive drugs, particularly BUS (−62%), IFN ((−62%), and ANA ((−68%). The use of the cytoreductive drugs was related to the patient mean age (years): BUS (76), PIPO (72), HU (67), ANA (53), IFN (48). In the patients diagnosed since the 2004 as compared with those before 2004, the mean age of the treated patients increased for BUS (from 69 to 81 yrs, p<0.001) and for HU (from 64 to 69 yrs, p<0.001) while it decreased for IFN (from 49 to 46 yrs, p<0.05). Conclusion: in the analyzed patients of the ET Italian registry the diagnosis appropriateness resulted improved in the cases observed since the year 2004 respect those observed before, with an increase of bone marrow biopsies from 51% to 68% of patients. Moreover, in accord with the ET therapy Italian guidelines, the use of the cytoreductive drugs was less frequent in the patients diagnosed since the year 2004 than before (particularly for BUS, IFN, and ANA) and the more safe molecules IFN and ANA were preferentially deserved to the younger patients.

Download Full-text

Faculty Opinions recommendation of Non-driver mutations in patients with JAK2V617F-mutated polycythemia vera or essential thrombocythemia with long-term molecular follow-up.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.732188943.793583129 ◽

2021 ◽

Author(s):

Ronald Hoffman

Keyword(s):

Polycythemia Vera ◽

Essential Thrombocythemia ◽

Driver Mutations

Download Full-text

Similar Rate of Thrombosis in Essential Thrombocythemia and Polycythemia Vera Patients after Stratification for JAK2 V617F Allele Burden.

Blood ◽

10.1182/blood.v112.11.1745.1745 ◽

2008 ◽

Vol 112 (11) ◽

pp. 1745-1745

Author(s):

Alessandra Carobbio ◽

Guido Finazzi ◽

Elisabetta Antonioli ◽

Paola Guglielmelli ◽

Alessandro M. Vannucchi ◽

...

Keyword(s):

Polycythemia Vera ◽

Essential Thrombocythemia ◽

Vascular Complications ◽

Jak2 V617f ◽

Similar Rate ◽

Wild Type ◽

Allele Burden ◽

Real Time Quantitative Pcr ◽

Venous Thromboembolic

Abstract Patients with Essential Thrombocythemia (ET) can be categorized as either JAK2 V617F mutated (V617F+) or wild type (V617F−). Mutated patients display multiple features resembling Polycythemia Vera (PV), with significantly higher hemoglobin level and neutrophil counts, lower platelet count, more pronounced bone marrow erythropoiesis and granulopoiesis and higher tendency to transform in PV. Presence of the mutation and/or allele burden has been variably associated with the rate of vascular complications in ET and PV, but a direct comparison between the two disorders under this respect has not been performed. To tackle this issue, we compared the rate of major thrombosis in 867 ET patients (57% were JAK2 V617F+) with that in 415 PV patients (all V617F+). The median follow-up was 4.9 (0 – 39) and 3.8 (0 – 26) years in ET and PV, respectively. High risk ET patients (age ≥ 60 years and/or previous thrombosis) received Hydroxyurea whereas the vast majority of low-risk remained untreated. PV patients were treated according to the current risk-stratified recommendations. Thrombotic episodes were recorded over time and calculated as rates % per patient/year (pt/yr). After adjusting for age, the thrombosis-free survival curves of JAK2 V617F+ and V617F− ET patients were superimposable until 10 years after the diagnosis, then they diverged so that the actuarial probability of major thrombosis in mutated ET patients reached that of PV (48% vs 55%, test for trend p=0.05). We found that JAK2 V617F+ allele burden measured by real-time quantitative PCR influenced these rates in a comparable way in both ET and PV. Actually, in JAK2 wild type ET (n=376, 43%) the rate was 1.4% pt/yr. In ET patients with JAK2 V617F+ allele burden ranging from 1 to 25% (N=190; 49%) the rate was 1.9 % pt/yr compared to 1.2 in PV patients (N=64, 19%); in the group with 26–50% the rate was 2.0 % pt/yr in ET (N=177; 45%) and 3.0 in PV patients (N=118, 36%); in cases of V617F+ allele burden greater than 50% the rate was 3.8 % pt/yr in ET (N=23; 6%) and 2.9 in PV patients (N=147, 45%). In conclusion, from this retrospective analysis, we conclude that in patients with ET harboring JAK2 V617F mutation the rate of stroke, myocardial infarction and venous thromboembolic complications is similar to that of PV patients and increases in dependence of V617F allele burden, supporting the hypothesis that ET and PV may be viewed as a continuum also in terms of vascular complications

Download Full-text

How the Real-Life Diagnostic and Therapeutic Approach Changed in the Last Two Decades in the Thrombocythemic Patients with Ph- Negative Myeloproliferative Neoplasm. Report on 2388 Subjects of the Registro Italiano Trombocitemie (RIT)

Blood ◽

10.1182/blood.v128.22.5472.5472 ◽

2016 ◽

Vol 128 (22) ◽

pp. 5472-5472

Author(s):

Luigi Gugliotta ◽

Alessandra Iurlo ◽

Gabriele Gugliotta ◽

Alessia Tieghi ◽

Lucia Canafoglia ◽

...

Keyword(s):

Therapeutic Approach ◽

Myeloproliferative Neoplasm ◽

Real Life ◽

High Standard ◽

Diagnostic Process ◽

First Year ◽

Thrombotic Risk ◽

Group I ◽

Group Ii

Abstract Background: the Registro Italiano Trombocitemie (RIT) was activated mainly to evaluate the diagnosis and therapy appropriateness in the thrombocythemic patients with Ph-negative myeloproliferative neoplasm (MPN) observed in the adhering centers. Objective: to evaluate how the diagnostic and therapeutic approach changed in the RIT patients diagnosed with thrombocythemic MPN in the last two decades. Methods: the RIT centers registered by a web-based system during the years 2005-2014 their thrombocythemic MPN patients, and semesterly updated their follow-up data. For patients diagnosed before 2005, the data on diagnosis and prior follow-up were retrospectively collected. The diagnostic process and the initial treatment (started into the first year after diagnosis) were comparatively analyzed in the patients diagnosed before and after 2005. Results: the RIT centers registered 2629 patients. 2388 of them, object of this analysis, were diagnosed between1995 and 2014: 1098 (46%) in the decade 1995-2004 (Group I), and 1290 (54%) in the decade 2005-2014 (Group II). The diagnostic process in the patients of Group II and Group I included bone marrow biopsy (BMB, performed into 1 year and before any cytoreduction): 85% vs 80%, p <0.001; clonality tests (JAK2 and/or others): 80% vs 9%, p<0.001; cytogenetic evaluation: 55% vs 57%, p 0.58; abdominal echography: 46% vs 41%, p 0.016. The patients of Group II, as compared with those of Group I, showed a similar gender distribution (M/F ratio 0.61 vs 0.65, p 0.452), and had at diagnosis: a higher age (median 60 vs 57 years, p <0.001; age >60 years in 50% vs 45% of cases, p <0.01); a similar rate of prior thrombosis (19% vs 19%), prior hemorrhage (3% vs 4%), CVRFs 69% vs 66%), splenomegaly (25% vs 25%), and hepatomegaly (22% vs 24%); a lower rate of disease-related symptoms (36% vs 40%, p 0.04); a higher rate of comorbidities (55% vs 51%, p 0.03). Moreover, they had: a lower platelet (PLT) count (median 737 vs 775 x 109/L, p <0.001; <600 x 109/L in 22% vs 14% of cases, p <0.001); a similar white blood cell (WBC) count (median 8.6 vs 8.5 x 109/L; >10 x 109/L in 28% vs 26% cases); a similar median levels of hematocrit (HCT %, in females 41.4 vs 41.0; in males 44.7 vs 44.6) and hemoglobin (Hb g/dL, in females 13.8 vs 13.6; in males 15.0 vs 14.9). The BMB, revised according to the WHO 2008 criteria, showed a not different distribution (p 0.21) of ET (64% vs 61%), ep-PMF (16% vs 17%), PMF (3% vs 2%), PV (4% vs 4%), and U-MPN (13% vs 16%. The JAK2 V617F mutation in patients of Group II (at diagnosis) and of Group I (after diagnosis) was found in 62% and in 58% of tested cases (p 0.054), respectively. The patients at high standard thrombotic risk were 58% vs 52%, p 0.004. In the patients of Group II and Group I the distribution of the treatment started into the first year was significantly different (p<0.001): AntiPLT 29% vs 24%, CYT 13% vs 16%, CYT+AntiPLT 49% vs 46%, CYT ± AntiPLT 62% vs 62%, AntiPLT ± CYT 78% vs 69%. The treatment CYT ± AntiPLT was started in the patients at high standard thrombotic risk with a rate of 81% vs 80%, respectively, and in the patients at low standard thrombotic risk in 37% vs 43% of cases, respectively. The initial treatment CYT±AntiPLT was related, in multivariate analysis, both in patients of Group II and Group I, with older age (>60 and 40-60 vs <40 years, p <0.001), higher PLT count (>1000 and 700-1000 vs <700 x 109/L, p <0.001), prior thrombosis (p <0.001), symptoms (p <0.001). Noteworthy, no relationship was found with JAK2 mutation, and WHO diagnosis. Conclusion: in the studied thrombocythemic MPN patients the real-life diagnostic approach was improved after 2005 not only due to the routine use of JAK2 tests, but also due to the higher rate of BMB done (85% vs 80%). The appropriateness of the cytoreductive treatment (CYT±AntiPLT started into one year from diagnosis) remained high in patients at high standard thrombotic risk (over 80% of cases were treated). Concomitantly, the inappropriate use of the cytoreductive drugs in patients at low standard thrombotic risk appreciably decreased (from 43% to 37% of cases). Moreover, it has to be remarked that the therapeutic approach was significantly influenced not only by older age and prior thrombosis, but also by thrombocytosis (PLT count >700 x 109/L), disease-related symptoms, and inconstantly by leukocytosis and CVRFs. Table Table. Disclosures Gugliotta: SHIRE Co.: Honoraria. Gugliotta:Bristol Myers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria.

Download Full-text

Non-driver mutations in patients with JAK2V617F-mutated polycythemia vera or essential thrombocythemia with long-term molecular follow-up

Annals of Hematology ◽

10.1007/s00277-017-3193-5 ◽

2017 ◽

Vol 97 (3) ◽

pp. 443-451 ◽

Cited By ~ 12

Author(s):

Alicia Senín ◽

Concepción Fernández-Rodríguez ◽

Beatriz Bellosillo ◽

Laura Camacho ◽

Raquel Longarón ◽

...

Keyword(s):

Polycythemia Vera ◽

Essential Thrombocythemia ◽

Driver Mutations

Download Full-text

Role of Non-Driver Mutations and JAK2V617F Allele Burden in Myelofibrotic and Acute Myeloid Transformation of Patients with Polycythemia Vera and Essential Thrombocythemia

Blood ◽

10.1182/blood.v128.22.1952.1952 ◽

2016 ◽

Vol 128 (22) ◽

pp. 1952-1952 ◽

Cited By ~ 2

Author(s):

Alicia Senín ◽

Conchi Fernández ◽

Beatriz Bellosillo ◽

Laura Camacho ◽

Raquel Longaron ◽

...

Keyword(s):

Multivariate Analysis ◽

Essential Thrombocythemia ◽

Chronic Phase ◽

Progressive Increase ◽

Driver Mutations ◽

Evolutionary Pattern ◽

Allele Burden ◽

Jak2v617f Allele Burden ◽

Acute Myeloid

Abstract Background: Non-driver mutations and JAK2V617F allele burden have been involved in progression to myelofibrosis (MF) or acute myeloid leukemia (AML) in patients with polycythemia vera (PV) and essential thrombocythemia (ET). It is unknown if both mechanisms play a different role in disease transformation and if they are useful in routine clinical practice. Methods: JAK2V617F allele burden was monitored in 208 patients (PV n=106, ET n=102) for a median of 6.5 years (range: 1-13). Quantification of JAK2V617F allele burden was assessed on the first available sample and every year thereafter. The evolutionary pattern of JAK2V617F allele burden was categorized as persistently low (<50%), persistently high (>50%), progressive increase (> 25% from baseline) or unexplained decrease (not therapy related). Next generation sequencing (NGS) analysis of 51 myeloid-related genes was performed in 100 patients with a median molecular follow-up of 10 years including all cases with transformation to AML or MF. Detected mutations by NGS in the last sample were studied in first paired sample obtained in the chronic phase (median time from diagnosis: 1.6 years). Time to myelofibrosis and time to AML were calculated according to the presence of non-driver mutations or the JAK2V617F evolutionary pattern. Multivariate analysis was performed by Cox regression. Results: With a median follow-up of 13 years (range: 1-30) 32 patients died whereas 24 and 12 patients progressed to MF and AML, respectively. Median age at diagnosis was 63 years (range: 20-94), 115 were women (55%) and 173 (83%) received cytoreduction. A persistently low JAK2V617F allele burden was observed in 62% of patients whereas the remainder presented a persistently high (25%), a progressive increase (11%) or a non-therapy-related decrease of JAK2V617F allele burden (2%). Non-driver mutations were detected in last sample in 48% of patients. Median number of mutations was 1 (range: 1-5). Mutational frequencies were: TET2 12%, DNMT3A 12%, TP53 9%, ASXL1 7%, RUNX1 4%, SF3B1 4%, SRSF2 4%, IDH1/2 4%, SH2B3 3 % and <2% for EZH2, ZRSR2, SETBP1, FLT3, NPM, BCOR, CBL, PTPN11, KAT6A, NF1, U2AF1, GNAS, PHF6, KTM2A, JAK2, BCORL1, NOTCH1, MPL and PRPF40B. Mutations were detected in first sample in 28% of patients (58% of those with mutations in last sample). Frequencies of mutations in first sample were: TET2 10%, DNMT3A 5%, TP53 5%, ASXL1 4%, SRSF2 4%, IDH1/2 3%, and < 2% for SF3B1, SH2B3, KMT2A and ZRSR2. The evolutionary pattern of JAK2V617F allele burden was not associated with the presence of mutations in first or last sample. Twelve patients progressed to AML (post-PV n=7, post-ET n=5), nine of them presented mutations in first sample. AML transformation at 15 years was 27% and 6.8% for patients with and without additional mutations in first sample, respectively (p=0.001). Mutated genes associated with a higher probability of AML transformation were DNMT3A (p<0.0001), SRSF2 (p<0.0001) and IDH (p<0.0001). Other variables associated with a higher probability of AML were age > 65 years (p=0.012) and exposure to busulfan (p=0.003). Evolutionary JAK2V617F pattern was not associated with the probability of AML (p=0.667). In multivariate analysis, an increased risk of AML transformation was observed for patients with additional mutations in the chronic phase (HR: 6.3; 95%CI 1.6-24.7, p=0.008) after adjusting for initial diagnosis, age and exposure to busulfan. Twenty-four MF transformations were documented (post-PV n= 18, post-ET n=6). Presence of additional mutations was not associated with the probability of MF (p=0.189). Patients with persistently high or a progressive increase of the JAK2V617Fallele burden showed a higher probability of MF transformation (24% versus 1.5% at 10 years, p<0.0001) that persisted in multivariate analysis after correction for age and initial diagnosis (HR 13.9, 95%CI: 2.9-65.6, p=0.001). Conclusion: Non-driver mutations are involved in the progression of PV and ET to AML but not to MF. NGS could be useful for identifying patients with PV or ET at risk of AML transformation. Acknowledgment:This work was supported by grants from the Instituto de Salud Carlos III, Spanish Health Ministry, FISPI13/00557, FISPI1300393, RD012/0036/0004, 2014 SGR567. Alicia Senín received a grant from Sociedad Española de Hematología y Hemoterapia. Disclosures No relevant conflicts of interest to declare.

Download Full-text

CAL2 Monoclonal Antibody Is a Rapid and Sensitive Assay for the Detection of Calreticulin Mutations in Essential Thrombocythemia and May Provide Prognostic Informations

Blood ◽

10.1182/blood.v128.22.3122.3122 ◽

2016 ◽

Vol 128 (22) ◽

pp. 3122-3122

Author(s):

Massimiliano Bonifacio ◽

Rachele Montemezzi ◽

Alice Parisi ◽

Giovanna De Matteis ◽

Luigi Scaffidi ◽

...

Keyword(s):

Monoclonal Antibody ◽

Essential Thrombocythemia ◽

Triple Negative ◽

Type A ◽

Driver Mutations ◽

Type B ◽

Term Outcome ◽

Long Term Outcome ◽

Calr Mutations

Abstract Background. Calreticulin (CALR) mutations are detected in the majority of JAK2 wild-type (wt) patients with Essential Thrombocythemia (ET) or Primary Myelofibrosis (MF). At variance with JAK2 and MPL point mutations, CALR mutations are highly heterogeneous, with several types of insdel reported to date, so that sequencing techniques are needed to cover the whole spectrum of mutations. CAL2 is a new monoclonal antibody specifically recognizing the C-neoterminal peptide derived from all the frameshift mutations of CALR. Methods. We retrospectively analyzed 172 ET patients followed at our Institution from 1980 to 2015 who were tested for JAK2V617F at the time of diagnosis or during follow-up. In JAK2wt patients exon 9 CALR mutations were searched by PCR and capillary electrophoresis and MPLW515L/K by ARMS-PCR. In the same patients, bone marrow (BM) biopsies were immunostained with CAL2 and histologically reviewed for megakaryocytic features. Results. Median age at diagnosis was 54 years (range 14-87) and median time from first evidence of thrombocytosis to BM biopsy was 8.4 months (range 0-175). According to driver mutations, patients were classified as JAK2V617F-mutated (n=119, 69%), MPL-mutated (n=2, 1%), CALR-mutated (n=31, 18%) or triple-negative (n=20, 12%). As expected, CALR-mutated patients had significantly higher platelet count than JAK2V617F (799 vs 657 x 109/L, respectively; p=.019) and lower hemoglobin values (mean 13.6 vs 14.5 g/dL, respectively; p=.003). At a median follow-up of 9.8 years, incidence of thrombosis was significantly lower in CALR- than in JAK2V617F-mutated patients (3% vs 21%, respectively; p=.017), while no differences were observed in clinical presentation and long-term outcome between CALR-mutated and triple-negative patients. Concordance between molecular and immunohistochemical (IHC) detection of CALR mutations was optimal (CohenÕs kappa >0.8) but not complete, since 3 patients were positive by IHC only and 1 patient was positive by molecular only. In CAL2-positive BM samples (n=30) we defined 2 patterns (figure), characterized by staining of megakaryocytes only (pattern A, 37%) or staining of megakaryocytes and myeloid precursors (pattern B, 63%). Type B biopsies tended to have higher median cellularity (48% vs 30%; p=.22), higher median megakaryocytic number for HMF (20 vs 12.5; p=.14), higher frequency of megakaryocytic clusters (100% vs 60%; p=.014) and higher frequency of grade-1 fibrosis (81% vs 60%; p=.37) with respect to type A samples. One type A patient and 2 type B patients progressed to post-ET MF or acute leukemia. Moreover, 3 patients had a BM biopsy performed at the time of MF evolution but not at diagnosis of ET, and they displayed a type B pattern. Conclusions. CAL2 identifies CALR-mutated ET patients in a rapid, sensitive, specific and economic manner and it integrates molecular biology informations. Prognostic value of different IHC patterns should be confirmed in wider and indipendent series. Figure Immunohistochemical patterns of CAL2 staining in ET samples: megakaryocytes only (pattern A) or megakaryocytes and myeloid precursors (pattern B). Figure. Immunohistochemical patterns of CAL2 staining in ET samples: megakaryocytes only (pattern A) or megakaryocytes and myeloid precursors (pattern B). Disclosures Bonifacio: Ariad Pharmaceuticals: Consultancy; Amgen: Consultancy; Bristol Myers Squibb: Consultancy; Pfizer: Consultancy; Novartis: Research Funding.

Download Full-text