Alexandra P. Wolanskyj

JAK2V617F mutation in essential thrombocythaemia: clinical associations and long-term prognostic relevance

Clinical correlates and long‐term prognostic relevance of the JAK2V617F mutation was studied in 150 patients with essential thrombocythaemia (ET) from a single institution and followed for a median of 11·4 years. During this period, thrombotic complications were documented in 62 patients (41·3%) and transformation into acute myeloid leukaemia (AML), polycythaemia vera (PV), or myelofibrosis with myeloid metaplasia (MMM) occurred in 4 (2·7%), 8 (5·3%), and 15 (10%) patients, respectively. JAK2V617F was detected in either archived bone marrow or blood cells from 73 patients (48·7%) but none were homozygous for the mutant allele. Parameters at diagnosis that were significantly associated with the presence of JAK2V617F included advanced age and higher counts of both haemoglobin and leucocytes. During follow‐up, patients with the mutation were more likely to transform into PV but the incidences of AML, MMM, or thrombotic events were similar between patients with and without the mutation. Multivariate analysis identified advanced age, higher haemoglobin level, and thrombosis history but not the presence of JAK2V617F as independent predictors of inferior survival. Therefore, although the presence of JAK2V617F in ET appears to promote a PV phenotype, it might not carry treatment‐relevant information.

Essential Thrombocythemia Beyond the First Decade: Life Expectancy, Long-term Complication Rates, and Prognostic Factors

OBJECTIVE To describe the long-term natural history of essential thrombocythemia (ET) in terms of life expectancy, risk of disease transformation Into a more aggressive myeloid disorder, and prognostic factors for both survival and disease complications. PATIENTS AND METHODS The study population consisted of a consecutive cohort of patients seen at the Mayo Clinic In Rochester, Minn, in whom a diagnosis of ET was established before 1992, thus allowing a minimum of 10 years of potential follow-up. The conventional criteria-based diagnosis was confirmed by bone marrow biopsy in all Instances. RESULTS A total of 322 patients were studied (median age, 54 years; median follow-up, 13.6 years). With a median survival time of 18.9 years, survival in the first decade of disease was similar to that of the control population (risk ratio, 0.72; 95% confidence interval, 0.50-0.99) but became significantly worse thereafter (risk ratio, 2.21; 95% confidence Interval, 1.74-2.76). Multivariable analysis identified age at diagnosis of 60 years or older, leukocytosis, tobacco use, and diabetes mellitus as Independent predictors of poor survival. A 2-variable model based on an age cutoff of 60 years and leukocyte count of 15 x 10(9)/L resulted in 3 risk groups with significant difference in survival. In addition, age at diagnosis of 60 years or older, leukocytosis, and history of thrombosis were independent predictors of major thrombotic events. The risk of leukemic or any myeloid disease transformation was low in the first 10 years (1.4% and 9.1%, respectively) but increased substantially in the second (8.1% and 28.3%, respectively) and third (24.0% and 58.5%, respectively) decades of the disease. CONCLUSION Life expectancy in patients with ET is significantly worse than that of the control population. Leukocytosis is identified as a novel independent risk factor for both inferior survival and thrombotic events.

Risk stratification for survival and leukemic transformation in essential thrombocythemia: a single institutional study of 605 patients.

Unlike the case with thrombosis, prognostic models for survival and leukemic transformation (LT) in essential thrombocythemia (ET) are not available. Among 605 patients with ET seen at our institution and followed for a median of 84 months, 155 died and LT was documented in 20 patients (3.3%). In a multivariable analysis, hemoglobin level below normal (females<120 g/l; males<135 g/l) was identified as an independent risk factor for both inferior survival and LT. Additional risk factors for survival included age ⩾60 years, leukocyte count⩾15 × 109/l, smoking, diabetes mellitus and thrombosis. For LT, platelet count⩾1000 × 109/l but not cytoreductive therapy was flagged as an additional independent risk factor. In fact, four of the 20 patients (20%) with LT were untreated previously. We used the above information to construct prognostic models that effectively discriminated among low-, intermediate- and high-risk groups with respective median survivals of 278, 200 and 111 months (P<0.0001), and LT rates of 0.4, 4.8 and 6.5% (P=0.0009) respectively. Presence of JAK2V617F did not impact either survival or LT and mutational frequency was similar among the different risk groups.

Type 1 versus Type 2 calreticulin mutations in essential thrombocythemia: A collaborative study of 1027 patients

CALR (calreticulin) trails JAK2 as the second most mutated gene in essential thrombocythemia (ET). Mutant CALR in ET is a result of frameshift mutations, caused by exon 9 deletions or insertions; type‐1, 52‐bp deletion (p.L367fs*46), and type‐2, 5‐bp TTGTC insertion (p.K385fs*47) variants constitute more than 80% of these mutations. The current study includes a total of 1027 patients divided into test (n = 402) and validation (n = 625) cohorts. Among the 402 ET patients in the test cohort, 227 (57%) harbored JAK2, 11 (3%) Myeloproliferative leukemia virus oncogene (MPL), and 114 (28%) CALR mutations; 12% were wild‐type for all three mutations (i.e., triple‐negative). Among the 114 patients with CALR mutations, 51 (45%) displayed type‐1 and 44 (39%) type‐2 variants; compared to mutant JAK2, both variants were associated with higher platelet and lower hemoglobin and leukocyte counts. However, male sex was associated with only type‐1 (P = 0.005) and younger age with type‐2 (P = 0.001) variants. Notably, platelet count was significantly higher in type‐2 vs. type‐1 CALR‐mutated patients (P = 0.03) and the particular observation was validated in the validation cohort that included 111 CALR‐mutated ET patients (P = 0.002). These findings, coupled with the recent demonstration of preferential expression of mutant and wild‐type CALR in megakaryocytes, suggest differential effects of CALR variants on thrombopoiesis. Am. J. Hematol. 89:E121–E124, 2014.

Concomitant neutrophil JAK2V617F mutation screening and PRV-1 expression analysis in myeloproliferative disorders and secondary polycythaemia

Polycythaemia vera (PV) is closely associated with both an acquired activating mutation of the JAK2 tyrosine kinase (JAK2V617F) in granulocyte‐derived DNA and increased granulocyte polycythaemia rubra vera‐1 (PRV‐1) expression. In order to explore the correlation between these two biological markers and compare their diagnostic utility, mutation analysis for JAK2V617F and quantitative measurement of granulocyte PRV‐1 expression were performed on the same study sample from 100 participants: 38 with PV, 22 with essential thrombocythaemia (ET), 10 with agnogenic myeloid metaplasia (AMM), 19 with secondary polycythaemia (SP) and 11 healthy volunteers. The respective overall (homozygous) JAK2V617F mutational frequencies were 95% (26%), 55% (0%), 30% (0%), 0% and 0%. The corresponding figures for increased PRV‐1 expression were 89%, 18%, 20%, 21% and 9%. In patients with either ET or AMM, the likelihood of detecting JAK2V617F was significantly higher in the presence of an increased PRV‐1 expression (83% vs. 38%; P = 0·05). Similarly, in patients with PV, homozygous as compared with heterozygous JAK2V617F correlated with higher levels of PRV‐1 expression (P = 0·11). The present study suggests an allele dose‐dependent effect of JAK2V617F on granulocyte PRV‐1 expression. However, compared with the PRV‐1 assay, mutation screening for JAK2V617F displayed greater accuracy in distinguishing PV from SP.

Calreticulin mutations and long-term survival in essential thrombocythemia

The impact of calreticulin (CALR) mutations on long-term survival in essential thrombocythemia (ET) was examined in 299 patients whose diagnosis predated 2006. Mutational frequencies were 53% for Janus kinase 2 (JAK2), 32% for CALR and 3% for MPL; the remaining 12% were ‘triple-negative’. We confirmed the association of mutant CALR (vs JAK2V617F) with younger age (P=0.002), male sex (P=0.01), higher platelet count (0.0004), lower hemoglobin (P<0.0001), lower leukocyte count (0.02) and lower incidence of recurrent thrombosis (0.04). Triple-negative patients were also younger than their JAK2-mutated counterparts (P=0.003) and displayed lower hemoglobin (P=0.003), lower leukocyte count (<0.0001) and lower thrombotic events (P=0.02). Median follow-up time was 12.7 years and 47% of the patients were followed until death. Survival was the longest for triple-negative and shortest for MPL-mutated patients. Median survival was 19 years for JAK2 and 20 years for CALR-mutated cases (P=0.32); the corresponding figures for patients of age ⩽65 years were 26 and 32 years (P=0.56). The two mutational categories were also similar for leukemic (P=0.28) and fibrotic (P=0.28) progression rates. The current study is uniquely characterized by its very long follow-up period and provides accurate estimates of long-term survival in ET and complements current information on mutation-specific phenotype and prognosis.

Prognostic Factors and Outcomes of Adults With Hemophagocytic Lymphohistiocytosis

OBJECTIVE To describe the prognostic factors and outcomes of adults with hemophagocytic lymphohistiocytosis (HLH), a rare disorder caused by pathologic activation of the immune system. PATIENTS AND METHODS The study population consisted of a consecutive cohort of adult (age ≥18 years) patients treated at Mayo Clinic in Rochester, Minnesota, from January 1, 1996, through December 31, 2011, in whom a diagnosis of HLH was suspected and subsequently confirmed by retrospective review using the HLH-04 diagnostic criteria. RESULTS Of 250 adult patients suspected of having HLH, 62 met the HLH-04 diagnostic criteria and were included in the final analysis. The median age was 49 years (range, 18-87 years), and 42 (68%) were male. The underlying cause of HLH was malignant tumor in 32 patients (52%), infection in 21 patients (34%), autoimmune disorder in 5 patients (8%), and idiopathic disease in 4 patients (6%). After a median follow-up of 42 months, 41 patients (66%) had died. The median overall survival of the entire cohort was 2.1 months. The median overall survival of patients with tumor-associated HLH was 1.4 months compared with 22.8 months for patients with non-tumor-associated HLH (P=.01). The presence of a malignant tumor and hypoalbuminemia were significant predictors of inferior survival on multivariate analysis. CONCLUSION In this large series of adults with secondary HLH treated at a single tertiary care center, patients with low serum albumin levels and tumor-associated HLH had a markedly worse survival. Hemophagocytic lymphohistiocytosis remains elusive and challenging to clinicians who must maintain a high index of suspicion. The recent discovery of several novel diagnostic and therapeutic modalities may improve outcomes of adult patients with HLH.

The JAK2 46/1 haplotype confers susceptibility to essential thrombocythemia regardless of JAK2V617F mutational status-clinical correlates in a study of 226 consecutive patients

The germline JAK2 haplotype 46/1, tagged by the ‘C’ allele of single-nucleotide polymorphism (SNP) rs12343867 (C/T), has been associated with JAK2V617F (VF)-positive myeloproliferative neoplasms. SNP rs12343867 was genotyped using bone marrow DNA in 226 consecutive patients with essential thrombocythemia (ET) with concomitant analysis of VF allele burden. The incidence of the 46/1-linked C allele was significantly higher in ET (genotype: CC 15%, CT 52%, TT 33%; C-allele frequency: 41%) than in population controls (P<0.01). Genotype distributions were similar among VF-positive/VF-negative patients (genotype: CC 18/11%, CT 52/53%, TT 30/36%; C-allele: 44/38%; P=0.29). Haplotype 46/1 frequency was remarkably similar when comparing VF-negative patients to those with <10% VF allele burden, but significantly higher in the presence of >10% VF allele burden (genotype: CC 11/13/38%, CT 53/56/38%, TT 36/31/24%; C-allele frequency: 38/41/57%; P<0.01). The clinical features of 46/1-positive and -negative ET were indistinguishable, including blood counts, rate of thrombosis/disease transformation and survival. We conclude that JAK2 haplotype 46/1 confers susceptibility to developing ET independent of VF mutational status and does not seem to further affect the clinical phenotype or prognosis.

Predictors of pregnancy outcome in essential thrombocythemia : a single institution study of 63 pregnancies

An increased risk of pregnancy complications was recently reported in JAK2V617F‐positive essential thrombocythemia (ET). In the current study of 63 pregnancies among 36 women with ET, we sought to appraise this association and identify other predictors of outcome. Overall outcome included 38 (60%) births and 20 (35%) first trimester spontaneous abortions. Among 36 first pregnancies, 22 (61%) resulted in live birth. Twelve of the 14 pregnancy losses occurred during the first trimester. Rate of pregnancy loss was 21% among 24 patients receiving aspirin therapy during the first trimester vs. 75% among 12 patients not receiving such treatment (P = 0.002). Pregnancy outcome was not influenced by platelet count, leukocyte count or presence of JAK2V617F; four pregnancy losses each were documented in 10 mutated and 10 unmutated patients. Among 17 second pregnancies, 12 (71%) resulted in live birth; these included eight from nine patients with successful and four from eight with unsuccessful first pregnancies (P = 0.07). Maternal complications were infrequent (11%): pre‐eclampsia (n = 1), hematoma after Cesarean‐section (n = 2) and post‐partum hemorrhage (n = 1). This study suggests a salutary role for aspirin therapy in pregnant women with ET. Furthermore, the occurrence of a miscarriage in ET might be a marker for a similar event during subsequent pregnancies.

Cytogenetic abnormalities in essential thrombocythemia: prevalence and prognostic significance

Objectives:  In the current study we describe cytogenetic findings as well as clinical correlates and long‐term prognostic relevance of abnormal cytogenetics at the time of diagnosis of essential thrombocythemia (ET).