Philadelphia chromosome-negative myeloproliferative neoplasms in younger adults: A critical discussion of unmet medical needs, with a focus on pregnancy

Essential thrombocythemia: 2024 update on diagnosis, risk stratification, and management

OVERVIEW

Essential thrombocythemia is a Janus kinase 2 (JAK2) mutation-prevalent myeloproliferative neoplasm characterized by clonal thrombocytosis; clinical course is often indolent but might be interrupted by thrombotic or hemorrhagic complications, microcirculatory symptoms (e.g., headaches, lightheadedness, and acral paresthesias), and, less frequently, by disease transformation into myelofibrosis (MF) or acute myeloid leukemia.

DIAGNOSIS

In addition to thrombocytosis (platelets ≥450 × 109 /L), formal diagnosis requires the exclusion of other myeloid neoplasms, including prefibrotic MF, polycythemia vera, chronic myeloid leukemia, and myelodysplastic syndromes with ring sideroblasts and thrombocytosis. Bone marrow morphology typically shows increased number of mature-appearing megakaryocytes distributed in loose clusters.

GENETICS

Approximately 80% of patients express myeloproliferative neoplasm driver mutations (JAK2, CALR, MPL), in a mutually exclusive manner; in addition, about 50% harbor other mutations, the most frequent being TET2 (9%-11%), ASXL1 (7%-20%), DNMT3A (7%), and SF3B1 (5%). Abnormal karyotype is seen in <10% of patients and includes +9/20q-/13q-.

SURVIVAL AND PROGNOSIS

Life expectancy is less than that of the control population. Median survival is approximately 18 years but exceeds >35 years in younger patients. The triple A survival risk model, based on Age, Absolute neutrophil count, and Absolute lymphocyte count, effectively delineates high-, intermediate-1-, intermediate-2-, and low-risk disease with corresponding median survivals of 8, 14, 21, and 47 years.

RISK FACTORS FOR THROMBOSIS

Four risk categories are considered: very low (age ≤60 years, no thrombosis history, JAK2 wild-type), low (same as very low but JAK2 mutation present), intermediate (same as low but age >60 years), and high (thrombosis history or age >60 years with JAK2 mutation).

MUTATIONS AND PROGNOSIS

MPL and CALR-1 mutations have been associated with increased risk of MF transformation; spliceosome with inferior overall and MF-free survival; TP53 with leukemic transformation, and JAK2V617F with thrombosis. Leukemic transformation rate at 10 years is <1% but might be higher in JAK2-mutated patients with extreme thrombocytosis and those with abnormal karyotype.

TREATMENT

The main goal of therapy is to prevent thrombosis. In this regard, once-daily low-dose aspirin is advised for all patients and twice daily for low-risk disease. Cytoreductive therapy is advised for high-risk and optional for intermediate-risk disease. First-line cytoreductive drugs of choice are hydroxyurea and pegylated interferon-α and second-line busulfan.

ADDITIONAL CONTENT

The current review includes specific treatment strategies in the context of extreme thrombocytosis, pregnancy, splanchnic vein thrombosis, perioperative care, and post-essential thrombocythemia MF, as well as new investigational drugs.

Clinical Features and Long-Term Outcomes of a Pan-Canadian Cohort of Adolescents and Young Adults with Myeloproliferative Neoplasms: A Canadian MPN Group Study

Myeloproliferative neoplasms (MPNs) are a group of chronic hematologic malignancies that lead to morbidity and early mortality due to thrombotic complications and progression to acute leukemia. Clinical and mutational risk factors have been demonstrated to predict outcomes in patients with MPNs and are used commonly to guide therapeutic decisions, including allogenic stem cell transplant, in myelofibrosis. Adolescents and young adults (AYA, age ≤45 years) comprise less than 10% of all MPN patients and have unique clinical and therapeutic considerations. The prevalence and clinical impact of somatic mutations implicated in myeloid disease has not been extensively examined in this population. We conducted a retrospective review of patients evaluated at eight Canadian centers for MPN patients diagnosed at ≤45 years of age. In total, 609 patients were included in the study, with median overall survival of 36.8 years. Diagnosis of prefibrotic or overt PMF is associated with the lowest OS and highest risk of AP/BP transformation. Thrombotic complications (24%), including splanchnic circulation thrombosis (9%), were frequent in the cohort. Mutations in addition to those in JAK2/MPL/CALR are uncommon in the initial disease phase in our AYA population (12%); but our data indicate they may be predictive of transformation to post-ET/PV myelofibrosis.

Polycythemia vera: 2024 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Polycythemia vera (PV) is a JAK2-mutated myeloproliferative neoplasm characterized by clonal erythrocytosis; other features include leukocytosis, thrombocytosis, splenomegaly, pruritus, constitutional symptoms, microcirculatory disturbances, and increased risk of thrombosis and progression into myelofibrosis (post-PV MF) or acute myeloid leukemia (AML).

DIAGNOSIS

A working diagnosis is considered in the presence of a JAK2 mutation associated with hemoglobin/hematocrit levels of >16.5 g/dL/49% in men or 16 g/dL/48% in women; morphologic confirmation by bone marrow examination is advised but not mandated.

CYTOGENETICS

Abnormal karyotype is seen in 15%-20% of patients with the most frequent sole abnormalities being +9 (5%), loss of chromosome Y (4%), +8 (3%), and 20q- (3%).

MUTATIONS

Over 50% of patients harbor DNA sequence variants/mutations other than JAK2, with the most frequent being TET2 (18%) and ASXL1 (15%). Prognostically adverse mutations include SRSF2, IDH2, RUNX1, and U2AF1, with a combined incidence of 5%-10%.

SURVIVAL AND PROGNOSIS

Median survival is ⁓15 years but exceeds 35 years for patients aged ≤40 years. Risk factors for survival include older age, leukocytosis, abnormal karyotype, and the presence of adverse mutations. Twenty-year risk for thrombosis, post-PV MF, or AML are ⁓26%, 16% and 4%, respectively.

RISK FACTORS FOR THROMBOSIS

Two risk categories are considered: high (age >60 years or thrombosis history) and low (absence of both risk factors). Additional predictors for arterial thrombosis include cardiovascular risk factors and for venous thrombosis higher absolute neutrophil count and JAK2V617F allele burden.

TREATMENT

Current goal of therapy is to prevent thrombosis. Periodic phlebotomy, with a hematocrit target of <45%, combined with once- or twice-daily aspirin (81 mg) therapy, absent contraindications, is the backbone of treatment in all patients, regardless of risk category. Cytoreductive therapy is reserved for high-risk disease with first-line drugs of choice being hydroxyurea and pegylated interferon-α and second-line busulfan and ruxolitinib. In addition, systemic anticoagulation is advised in patients with venous thrombosis history.

ADDITIONAL TREATMENT CONSIDERATIONS

At the present time, we do not consider a drug-induced reduction in JAK2V617F allele burden, which is often incomplete and seen not only with peg-IFN but also with ruxolitinib and busulfan, as an indicator of disease-modifying activity, unless accompanied by cytogenetic and independently-verified morphologic remission. Accordingly, we do not use the specific parameter to influence treatment choices. The current review also includes specific treatment strategies in the context of pregnancy, splanchnic vein thrombosis, pruritus, perioperative care, and post-PV MF.

Essential Thrombocythemia in Adolescents and Young Adults: Clinical Aspects, Treatment Options and Unmet Medical Needs

OPINION STATEMENT

Current treatment of essential thrombocythemia (ET) should primarily prevent thrombo-hemorrhagic events, without increasing the rate of fibrotic progression or leukemic evolution, and secondarily control microvascular symptoms. Unlike other classic BCR::ABL1-negative myeloproliferative neoplasms, ET is frequently diagnosed in adolescents and young adults (AYA), defined as individuals aged 15 to 39 years, in up to 20% of patients. However, since the current risk stratification of this disease is based on models, including that of ELN, IPSET-Thrombosis and its revised version, mainly applied to an older patients' population, international guidelines are needed that specifically consider how to evaluate the prognosis of AYAs with ET. Furthermore, although ET is the most frequent MPN among AYA subjects, there is a lack of specific recommendations on how to treat it in this subgroup of patients, as management decisions are typically extrapolated from those for the elderly. Accordingly, since AYAs with ET represent a unique disease subset defined by attenuated genetic risk, more indolent phenotype, and longer survival than their older counterparts, treatment selection requires special attention to specific issues such as the risk of fibrotic/leukemic transformation, carcinogenicity, and fertility. This review article will provide a comprehensive overview of the diagnosis, prognostic stratification, and possible therapeutic approaches for AYA patients with ET, including antiplatelets/anticoagulants and cytoreductive agents, with a focus on pregnancy management in real-life clinical practice.