Splicing Factor 3B Subunit 1 Mutations in Myelofibrosis

By Patrick Daly - Last Updated: September 26, 2023

In a presentation at the 2022 American Society of Clinical Oncology Annual Meeting, Prithviraj Bose and colleagues reported that mutations in splicing factor 3B subunit 1 (SF3B1) are an uncommon occurrence in patients with myelofibrosis and do not appear to substantially affect outcomes and disease phenotype.

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This finding is distinct from the effects of SF3B1 mutations in other myelodysplastic syndromes and myeloproliferative neoplasms, where they indicate a “unique phenotype” with a favorable prognosis, according to Dr. Bose.

The study retrospectively analyzed 381 patients with World Health Organization (WHO)-defined myelofibrosis who visited the authors’ center from January 2017 to July 2021. Patients with either SF3B1-mutated or SF3B1-wild type myelofibrosis were compared on the following variables: disease phenotype, myeloproliferative neoplasms driver and co-occurring mutations, cytogenetics, dynamic International Prognostic Scoring System (IPSS) score, transfusion requirements, treatment characteristics, and survival outcomes.

Of the 381 patients, 29 (8%) were SF3B1-mutated, with K666N being the most common mutation (52%). Overall frequencies of JAK2, CALR, MPL mutations, and triple negative myelofibrosis were similar between the SF3B1-mutated and non-mutated groups. Notably, more SF3B1-mutated patients were PRBC transfusion-dependent at presentation that non-mutated patients.

Ultimately, the authors concluded that SF3B1 mutations are rare in patients with myelofibrosis and, except for PRBC transfusion dependence, most measures between mutated and non-mutated groups were relatively similar.

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