Do Myelofibrosis, Essential Thrombocythemia Patients With CALR Mutations Have Lower Disease Risk?

By Rob Dillard - Last Updated: September 10, 2024

Patients with myelofibrosis (MF) or essential thrombocythemia (ET) with calreticulin (CALR) and janus kinase 1 (JAK2) mutations have a similar symptom burden, according to a study presented at the Society of Hematologic Oncology 2024 Annual Meeting in Houston, Texas.

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In this prospective observational study, investigators analyzed disease characteristics, treatment patterns, and disease progression of 881 patients with MF or ET with reported CALR or JAK2 mutations enrolled in the Myelofibrosis and Essential Thrombocythemia Observational Study (MOST) study. The patients were aged 18 years or older with low-risk primary or secondary MF, or they were aged 60 years or older with ET, or they had a history of a thromboembolic event or were receiving ET-directed treatment.

The findings showed that disease progression was similar for MF-CALR and MF-JAK2(50.0% vs 61.0%) and ET-CALR and ET-JAK2 patients (1.9% vs 4.6%). The investigators observed that leukemic transformation occurred in zero MF-CALR vs seven (5.7%) MF-JAK2, as well as six (5.8%) ET-CALR vs 36 (5.7%) ET-JAK2 patients. No CALR-positive patients, seven (5.7%) MF-JAK2, and 11 (1.8%) ET-JAK2 patients died of disease progression, the researchers noted.

“The investigators concluded that this study demonstrates similar symptom burden among CALR– and JAK2-positive patients. Although about 80% of CALR-positive patients received myeloproliferative neoplasm-directed treatment, blood counts were elevated at enrollment and symptoms were unchanged on study.”

Reference

Oh S, Pemmaraju N, Nathwani N, et al. Characteristics of patients with myelofibrosis and essential thrombocythemia who harbor a calreticulin (CALR) gene mutation: subanalysis of the MOST study. Abstract #MPN-099. Presented at the Society of Hematologic Oncology 2024 Annual Meeting; September 4-7, 2024; Houston, Texas.

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