MPN-077 Characteristics, Blood Counts, Treatments, and Clinical Outcomes of 3022 Patients With Polycythemia Vera (PV) Treated in US Community Practices.

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Cytoreduction with hydroxyurea (HU) is the recommended first-line (1L) treatment for high-risk PV (age ≥60 years; history of thrombosis), but many patients have a suboptimal response. To describe characteristics, blood counts, treatments, and clinical outcomes among patients with PV. Retrospective observational study of adults in The US Oncology Network iKnowMed electronic health record database with ≥2 post-PV diagnosis visits during the study (01JAN2008-31JAN2021). Suboptimal response was defined as meeting ≥1 of the following criteria after ≥3 months of HU treatment: (1) white blood cell (WBC) count >10×109/L, (2) platelet count >400×109/L, and/or (3) hematocrit (HCT) >45%. Duration of therapy and overall survival were assessed via Kaplan-Meier method. Overall, 3022 patients with PV were included (mean age at diagnosis, 65.8 years [69% ≥60 years]; female, 46%; White, 85%; current/former tobacco users, 49%). At diagnosis, 7% of patients had a history of thrombosis, and 71% had high-risk PV; 37% (886/2413), 32% (778/2411), and 67% (1617/2418) had elevated WBC (>10×109/L), platelets (>400×109/L), and HCT (>45%), respectively. Cytoreductive therapy as 1L treatment was received by 48% of patients (44% HU); phlebotomy data were unavailable. Five-year survival probability was 84% among all patients (low-risk [age <60 years; no history of thrombosis], 97%; high-risk, 81%). Among patients who received 1L HU (n=1317), median (Q1, Q3) time from diagnosis to HU initiation was 19 (0, 189) days; median (Q1, Q3) duration of HU was 30 (9.5, 64.4) months, and 29.5 (9.5, 58.5) and 35.0 (9.5, 77.0) months for high- and low-risk patients, respectively. Among patients on 1L HU with evaluable blood counts, 55% (584/1053) had a suboptimal response (WBC >10×109/L, 26%; platelets >400×109/L, 26%; HCT >45%, 36%) at 3 months; similar findings were seen at 6 months. Among patients with suboptimal response to 1L HU, 5-year survival probability was 87% (low risk, 100%; high risk, 84%). The prevalence of elevated blood counts at diagnosis and follow-up while on HU treatment is consistent with previous real-world experience. About 1 in 8 patients with a suboptimal response to HU died within 5 years.