Patients With Cytopenic Primary Myelofibrosis Face Unique Therapeutic Challenges, Poor Prognosis

February 12, 2025

Author(s): Luke Halpern, Assistant Editor

Patients with primary myelofibrosis (PMF) harboring the cytopenic phenotype called cytopenic (CyP) PMF face greater unmet needs and worsened prognosis compared with other myeloproliferative neoplasms (MPNs), including polycythemia vera (PV) and essential thrombocytopenia (ET), according to an analysis of data from the European multicenter collaborative ERNEST registry.1

Myelofibrosis that advances to blast phase worsens outcomes for patients affected. | Image Credit: © tonaquatic – stock.adobe.com

Disease behavior of MF can vary widely based on clinical phenotype. Two distinct subgroups comprise MF: proliferative MF and cytopenic MF, which is also called myelodepletive MF. For patients with cytopenic MF, disease presentation can encompass lower blood counts—specifically thrombocytopenia and anemia—additional somatic mutations, and a worse prognosis compared with proliferative MF.2

Additionally, approved Janus kinase (JAK) inhibitors that can improve constitutional symptoms of MF carry risks of worsening anemia and thrombocytopenia in CyP MF, making treatment uniquely challenging for patients. Severe anemia is known to further worsen patient prognosis, and measures to relieve disease burden, such as transfusions, can lead to disease progression into blast phase (BP) MF. Given the poor outcomes MF patients with CyP face, describing the clinical characteristics and outcomes of this population is critical.1,3

The current investigators analyzed data gathered from the European multicenter collaborative ERNEST registry, with a focus on the clinical outcomes and characteristics of MF patients with CyP. In total, 559 patients comprised the study population; a CyP was defined by the presence of at least 1 cytopenia at diagnosis, including sex-adjusted anemia, thrombocytopenia, or leukopenia. Patients who showed none of these characteristics were considered MyP.1

Median follow-up was 5.4 years. A CyP was identified in 275 patients (49.2%); these patients were more likely to be older, less frequently JAK2V617F-mutated, and included in higher risk categories. In total, 392 patients (70.1%) died, including 59.9% of MyP patients and 80.7% of CyP patients, and the incidence rate of death among patients with both anemia and thrombocytopenia was the highest among the subgroups analyzed.1

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Cytopenias/Proliferation Define Outcomes for Patients With Primary MF and MF from Essential Thrombocythemia or PV

Amber Denham

05/31/2024

According to research presented at the 2024 American Society of Clinical Oncology (ASCO) annual meeting, cytopenias and/or proliferation, rather than JAK2V617F (JAK2) allele burden </≥50%, correlate with the outcomes of patients with primary myelofibrosis (PMF) and patients with MF from essential thrombocythemia or polycythemia vera (PPV/PET-MF). In addition, all patients were noted to display improved survival with ruxolitinib treatment.

Myelodepleted MF, which is characterized by cytopenias, lower JAK2 allele burden, and shorter benefit from JAK-inhibitor ruxolitinib, exhibits worse overall survival (OS) compared to myeloproliferative MF. In addition, lower JAK2 and inferior OS is generally more typical for patients with primary MF (PMF) as compared with patients with MF from essential thrombocythemia or polycythemia vera (PPV/PET-MF).

“We sought to investigate the impact of JAK2 (</≥ 50%), cytopenias and the use of ruxolitinib in outcome of PMF/PPV-PET-MF patients from our center,” explained Julie Braish, MBBCh, The University of Texas MD Anderson Cancer Center, Houston, Texas and colleagues.

To determine these results, study authors retrospectively reviewed the medical charts of 601 patients with JAK2-mutated MF (known JAK2%). Patients were divided based on the absence (-) or presence (+) of cytopenias (hemoglobin < 10 g/dL or platelets < 100 x109/L) and leukocytosis (WBC ≥ 25 x109/L) into: grade 1 = (-)/(-) [absence of both]; grade 2 = (-)/(+) [proliferative]; grade 3 = (+)/(-) [cytopenic]; grade 4 = (+)/(+) [cytopenic and proliferative]) and evaluated overall survival (OS) per JAK2 </≥ 50% and PMF vs PPV/PET-MF. Investigators assessed the tolerance of ruxolitinib ≥3 years by utilizing descriptive statistics, Kaplan-Meier curve with log-rank test and regression analysis for demographics, estimation of OS and its comparison.

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