Real-world treatments and thrombotic events in polycythemia vera patients in the USA.

Polycythemia vera (PV) is a myeloproliferative neoplasm associated with increased risk of thrombotic events (TE) and death. Therapeutic interventions, phlebotomy and cytoreductive medications, are targeted to maintain hematocrit levels < 45% to prevent adverse outcomes. This retrospective observational study examined medical and pharmacy claims of 28,306 PV patients initiating treatment for PV in a data period inclusive of 2011 to 2019. Study inclusion required ≥ 2 PV diagnosis codes in the full data period, at least 1 year of PV treatment history, and ≥ 1 prescription claim and medical claim in both 2018 and 2019. Patients having ≥ 2 hematocrit (HCT) test results in linked outpatient laboratory data (2018-2019) were designated as the HCT subgroup (N = 4246). Patients were characterized as high- or low-risk at treatment initiation based on age and prior thrombotic history. The majority of patients in both risk groups (60% of high-risk and 83% of low-risk) initiated treatment with phlebotomy monotherapy, and during a median follow-up period of 808 days, the vast majority (81% low-risk, 74% high-risk) maintained their original therapy during the follow-up period. Hematocrit control was suboptimal in both risk groups; 54% of high-risk patients initiating with phlebotomy monotherapy sometimes/always had HCT levels > 50%; among low-risk patients, 64% sometimes/always had HCT levels above 50%. Overall, 16% of individuals experienced at least 1 TE subsequent to treatment initiation, 20% (n = 3920) among high-risk and 8% (n = 629) among low-risk patients. This real-world study suggests that currently available PV treatments may not be used to full advantage.