Characteristics, blood counts, treatments, and clinical outcomes of 3,022 patients (Pts) with polycythemia vera (PV) treated in U.S. community practices.

Abstract

e19076 Background: Cytoreduction with hydroxyurea (HU) is the recommended first-line (1L) treatment for high-risk PV (age ≥60 y or history of thrombosis), but many pts have a suboptimal response on HU. The objective of this study was to describe characteristics, blood counts, treatments, and clinical outcomes among pts with PV, including those with suboptimal response to HU, in a large network of US community oncology practices. Methods: This was a retrospective observational study of adult pts with a documented diagnosis of PV in The US Oncology Network iKnowMed electronic health record database. Pts with ≥2 post-diagnosis visits during the study observation period (01JAN2008–31JAN2021) were included in the analysis. Suboptimal response to HU was defined as meeting ≥1 of the following criteria after ≥3 months of treatment: (1) white blood cell (WBC) count > 10 × 109/L, (2) platelet count > 400 × 109/L, and/or (3) hematocrit (HCT) > 45%. Data on demographic and clinical characteristics and prior treatment were collected and summarized using descriptive statistics. Duration of therapy and overall survival were assessed via Kaplan-Meier method; pts without subsequent treatment discontinuation/death records were censored. Results: Overall, 3022 pts with PV were included in the analysis; mean age at diagnosis was 65.8 years (69% ≥60 y), 46% of pts were female, 85% were White, and 49% were current/former tobacco users. At diagnosis, 7% of pts had a history of thrombotic event, and 71% had high-risk PV; 37% (886/2413), 32% (778/2411), and 67% (1617/2418) of evaluable pts had elevated WBC (> 10 × 109/L), platelets (> 400 × 109/L), and HCT (> 45%), respectively. Nearly half of pts (48%) received a cytoreductive agent as 1L treatment (44% HU), and 52% did not receive cytoreductive therapy; phlebotomy data were unavailable. Five-year survival probability was 84% among all pts, 97% for low-risk pts (age < 60 y; no history of thrombosis), and 81% for high-risk pts. Among pts 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 overall, and 29.5 (9.5, 58.5) and 35.0 (9.5, 77.0) months for high- and low-risk pts, respectively. Among pts 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 pts with suboptimal response to 1L HU, 5-year survival probability was 87% overall (low risk, 100%; high risk, 84%). Conclusions: 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 pts with a suboptimal response to HU died within 5 years. HU dose adjustments or alternative treatments may be needed for pts with suboptimal response to HU.