Characteristics, blood counts, treatments, and clinical outcomes of 5871 patients with polycythemia vera treated in US community practices

Objective This study aimed to describe clinical characteristics-including blood counts and pharmacologic cytoreductive treatment patterns-and outcomes after 6 months of hydroxyurea (HU) treatment among patients with polycythemia vera (PV) in US community practices. Methods This retrospective observational study included adult patients with a PV diagnosis (1JAN2008-31JAN2020) and >= 2 postdiagnosis visits in the iKnowMed electronic health record database (US Oncology Network and non-Network clinics). Suboptimal HU response required >= 1 criterion after >= 3 months of treatment: white blood cell count (WBC) >10 x 10(9)/L, platelet count >400 x 10(9)/L, and/or hematocrit >45%. Patient characteristics were summarized from structured data using descriptive statistics; overall survival was assessed by Kaplan-Meier method. Results Among 5871 patients, mean age at diagnosis was 66.1 years (69.8% >= 60 years); 67.2, 59.4, 38.2, and 33.9% of patients had elevated hematocrit, hemoglobin, WBC, and platelets, respectively; 6.1% had a previous thrombotic event. Of 4185 (71.3%) high-risk and 1675 low-risk patients, 55.0 and 32.0% received pharmacologic cytoreductive treatment, most commonly HU (89.8 and 88.9%). After 6 months of pharmacologic cytoreductive treatment, 56.9% had a suboptimal response. Five-year survival probability was 81.5 and 84.3% among patients with suboptimal and optimal responses to HU, respectively, which was not statistically different but suggests potential for survival benefits with longer follow-up. Conclusion Nearly half of high-risk patients with PV did not receive pharmacologic cytoreductive treatment. Of those who did, over half had suboptimal response, suggesting these patients may need dose adjustments, improved adverse effect management, or alternative treatments. Longer follow-up may be needed to assess an association between HU response and survival.