Risk of thromboembolic events in patients with polycythaemia vera: a study based on german health claims data.

This retrospective cohort study evaluated thrombotic outcomes and treatment patterns in patients with polycythemia vera (PV) in German health claims data. Prevalent and incident patient populations were identified, and longitudinal cohorts were formed to assess thromboembolic event (TE) rates, phlebotomy frequency, and the development of hydroxyurea (HU) intolerance or resistance. Patients were stratified into four thrombotic risk categories based on prior TE, age ≥ 60 years, or both, with low risk defined as the absence of both risk factors. Between 2021 and 2023, approximately one-third of prevalent patients underwent phlebotomy annually, whereas incident patients required more frequent procedures. TE risk differed substantially by risk category: patients with event- and age-based high-risk had a 6.2-fold higher rate than low-risk patients (82.4 vs. 13.4 per 1,000 person-years). Both prior TE history and advanced age contribute to TE-risk. While age-based high-risk alone showed a slightly stronger effect than event-based high-risk (11.3% vs. 9.0%), patients with both risk factors had the highest TE incidence (21.1%), highlighting the clinical relevance of thromboembolic history beyond age alone. Among incident patients, TE-free survival declined from 91.9% at one year to 89.3% at three years post-diagnosis. During follow-up, 22% of HU-treated patients met proxy measures for intolerance or resistance to HU after a median of 337 days. These patients experienced higher TE rates compared to patients treated with ruxolitinib (72.9 vs. 46.7 per 1,000 person-years), although differences were not significant. This real-world analysis suggests a persistent TE risk in PV, particularly among TE-based high-risk patients, and supports the importance of risk-adapted monitoring and timely therapy optimization.