Prevalence of cytopenic myelofibrosis in the United States.

e18575 Background: Among patient (pts) with myelofibrosis (MF), cytopenias (anemia or thrombocytopenia) are a marker of advanced disease, associated with higher symptom burden, as well as a higher risk of leukemic transformation and death. Epidemiological data is lacking on the prevalence of MF, particularly those with cytopenic MF in the United States (US). Methods: Administrative claims data from the Optum Research Database (ORD) were used to select pts with MF (≥2 non-diagnostic claims for MF) and continuous enrollment for ≥6 months prior to and ≥12 months after diagnosis (unless deceased within 12 months of diagnosis) from July 2016 to April 2023. Cytopenic MF was defined as the presence of anemia or thrombocytopenia based on diagnostic codes in medical claims, at the time of MF diagnosis and prior to treatment initiation. Prevalence of MF was estimated by the number of pts with MF in ORD over a 4-year look-back period prior to December 31, 2022 with 12 months of enrollment in 2022, divided by the number of enrollees in ORD who had 12 months of enrollment in 2022. The prevalence of MF and cytopenic MF in the ORD was standardized to the US population by age, sex, and region using 2023 US census data overall and restricted to adults. Results: Of 12.4 million enrollees in ORD in 2022, 1,368 had MF. Among pts with MF, 48.8% were male, and 82.1% were ≥65 years of age. A majority of pts were cytopenic at diagnosis (73.8%) with a higher percentage with cytopenia at treatment initiation (85.5%). The prevalence of MF in ORD was 11.0 per 100,000 enrollees. Standardized to the US population, the estimated prevalence of MF was 6.3 per 100,000 people, and 4.5 per 100,000 people for cytopenic MF (Table). Prevalence estimates were higher when standardized to the US adult population ≥18 years of age for MF (8.0 per 100,000 people) and cytopenic MF (5.7 per 100,000 people) (Table). Standardized prevalence estimates for cytopenic MF were higher overall and among adults at the time of treatment initiation compared to at the time of MF diagnosis (Table). Standardized prevalence estimates of non-cytopenic MF were roughly half of the estimates for cytopenic MF (Table). Conclusions: Based on data from the ORD standardized to the US population, 21,133 pts were estimated to have MF in 2023 in the US, of which 70.8% had cytopenic MF at diagnosis and an additional 13% developed cytopenia at the start of treatment. These estimates are foundational to understanding the burden of disease in pts with MF in the US, including those with cytopenia and for supporting additional efforts in clinical research, education, treatment options, and health policy. Prevalence of MF in the US. Cytopenia at diagnosis Cytopenia prior to treatment MF Cytopenic Non-cytopenic Cytopenic Non-cytopenic US population* 6.3 4.5 1.8 5.3 1.0 US adult population* 8.0 5.7 2.3 6.7 1.3 *Per 100,000 people in 2023.