Phlebotomy, Cytoreductive Treatments Are Effective Yet Underused in Older Patients With PV

Guidelines indicate that high-risk patients with polycythemia vera (PV) should be treated with phlebotomy and cytoreductive therapy—such as hydroxyurea or interferon-alfa—to reduce the risk of thrombosis, the major cause of death among patients with PV. To assess the effectiveness of these treatment modalities among older US adults with PV, the authors of a newly published paper evaluated a large cohort of patients with PV in the real-world setting.

Using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database, the investigators assembled a retrospective cohort of 820 patients who were diagnosed with PV between 2007 and 2013. Two outcomes of interest were evaluated: overall survival (OS) and the occurrence of a thrombotic event after diagnosis.

The median age of the patients was 77 years (interquartile range, 71-83). During the study period, 41.1% received both phlebotomy and hydroxyurea, either concurrently or sequentially. Another 23.0% received phlebotomy only, 19.6% received hydroxyurea only, and 16.3% received neither. Other cytoreductive treatments were used infrequently; only 2% of patients receivedruxolitinib, and only 1.3% were treated with interferons.

After a median followup of 2.8 years, 305 patients (37.2%) died. The median survival was 6.29 years for those who received phlebotomy, and 4.50 years for those who did not. The median survival was 6.02 years for those who used hydroxyurea, and 5.25 years for those who did not.

Increasing phlebotomy intensity appeared to be associated with lower mortality (hazard ratio [HR], 0.71; 95% CI, 0.65-0.79; P <.01), and every 10% increase in the proportion of days covered for hydroxyurea treatment was associated with an 8% to 9% reduction in the risk of death. Advanced age, male sex, having 1 or more comorbidity, and underutilization of healthcare were all associated with increased mortality.

Thrombotic events were observed in 36.1% of patients (46.0% among those who did not receive phlebotomy versus 29.3% of those who received phlebotomy). Increasing phlebotomy intensity was also associated with a lower risk of thrombotic events (HR, 0.52; 95% CI, 0.42-0.66; P <.01).

The percentage of patients who had thrombotic events and who did not use hydroxyurea was 45.4% versus 27.6% among those who did use the therapy. Every 10% increase in the proportion of days covered for hydroxyurea treatment was also associated with an 8% lower risk of thrombosis.

Other factors that were associated with higher risk of thrombosis were having 2 or more comorbidities and receiving a low-income subsidy.

The authors concluded that OS improved and the risk of thrombosis decreased in older patients with PV who were treated with phlebotomy and hydroxyurea, but contrary to guidelines, both treatments were underused in this population, as only 64.0% and 60.6% received the 2 therapies, respectively. “Improved dissemination and implementation of the guidelines may translate to better patient outcomes,” said the authors.

Reference

Podolsev NA, Zhu M, Zeidan AM, et al. The impact of phlebotomy and hydroxyurea on survival and risk of thrombosis among older patients with polycythemia vera.Blood Adv.2018;2(20):2681-2690. doi: 10.1182/bloodadvances.2018021436.