Rates of Thrombosis in Patients Treated With Hydroxyurea Fairly Stable Over Time, Review Finds

A recent literature review and meta-analysis of patients treated with hydroxyurea, a standard treatment for polycythemia vera (PV), found a stable rate of thrombosis over time, although residual rates for these patients were higher than for the general population.

PV is a myeloproliferative neoplasm (MPN) characterized by high frequency of thrombosis and a tendency to transform into acute myelogenous leukemia (AML) or myelofibrosis (MF). Patients must be assessed for the potential risk of developing major thrombotic or hemorrhagic complications. High-risk patients are those over the age of 60 or with prior thrombotic complications.

After initially selecting 429 reports, the authors chose 16 studies of adults over 18 were chosen for review. The studies were published between 2008 to 2018. All the studies had at least 20 participants and were prospective and retrospective cohort studies. Case reports and narrative reviews were not included. In total, 3236 patients were analyzed. The review, published in Haematologica, used a random effect logistic model. Incidences, study heterogeneity, and confounder effects were estimated for each outcome at different follow ups.

Mortality and myelofibrosis varied depending on follow-up duration, but incidences of thrombosis and acute myeloid leukemia (AML) were stable over time. Overall incidence of thrombosis was about 3% per year, determined by pooling event rates from each study.

Thrombosis rates were 1.9%, 3.6% and 6.8% persons/year at median ages 60, 70 and 80 years, respectively, based on 2552 patients and 469 events. Mortality for the same intervals under the same conditions was 2.4%, 12.6%, and 56.2%.

Previous cardiovascular complication predicted higher incidence of bleeding, and cumulative AML incidence over 10 years was about 4%.

Incidence of transformation to MF and mortality were significantly dependent on age and follow-up duration. For myelofibrosis, rates were 5% at 5 years and 33.7% at 10 years; overall mortality was 12.6% and 56.2% at 5 and 10 years, respectively. The researchers noted that the estimates rise or fall with age at the start of follow up, with the odds of MF increasing on average 6% for each year of age, while those of death rise by 21%.

The researchers said their findings can help design comparative clinical trials with new critical end points for efficacy.

Reference

Ferrari A, Carobio A, Masciulli A, et al. Clinical outcomes under hydroxyurea treatment in polycythemia vera: A systematic review and meta-analysis. Haematologica.104(12): 2391-2399. doi:10.3324/haematol.2019.221234.