Rates of arterial and venous thrombosis are significantly elevated in patients with myeloproliferative neoplasms (MPNs) with the highest rates of thrombosis around the time of diagnosis of the bone marrow disease.
A Swedish cohort study of over 9,429 patients with diseases including polycythemia vera, essential thrombocythemia (ET) and primary myelofibrosis (PMF) quantified the level of risk of thrombosis compared to more than 35,000 matched controls.
The study found hazard ratios (HRs) for any thrombosis after any diagnosis started at 4.0 at three months, dropping to 2.4 at one year and 1.8 at five years.
A similar pattern of risk was found for arterial thrombosis (HR = 3.0 at three months, 2.0 at one year and 1.5 at five years) and for venous thrombosis (HR = 9.7 at three months, 4.7 at one year and 3.2 at five years).
Rates of thrombosis were significantly elevated in all age groups although the highest HR was found in the youngest patient group 18-49 years. The HR for thrombosis was similar in men and women.
“Overall, HRs were similar across MPN subtypes, which confirms previous findings of similar incidence of thrombosis in patients with ET and PMF and further emphasiszes that vascular events are major contributors to excess morbidity and mortality in patients with MPNs.”
The findings support ‘the importance of initiating phlebotomy as well as thromboprophylactic and cytoreductive treatment, when indicated, as soon as the MPN is diagnosed’, they said.
An accompanying editorial in Annals of Internal Medicine highlighted the magnitude of the thrombotic risk associated with MPNs.
It said the HRs for arterial events were similar to those for cigarette smoking, and for venous events they were akin to the elevated risks associated with factor V Leiden heterozygosity.
“Approximately 10% of patients with MPNs had a thromboembolic event within 30 days before or after diagnosis.”
“Patients and clinicians should be keenly aware of this particularly risky period, during which risk for thrombosis is similar to that in the month after a transient ischemic attack.”