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Risk for thrombosis in patients with myeloproliferative neoplasms was highest near the time of diagnosis

Question What is the risk for arterial and venous thrombosis in patients with myeloproliferative neoplasms (MPN)? Methods Design Inception cohort with matched controls followed for up to 20 years. Setting Sweden. Patients 9429 patients (median age at diagnosis 72 y, 54% women) with a new diagnosis of MPN included in the Swedish Cancer Register or Inpatient Register between 1987 and 2009. 35820 matched participants without MPN from the Total Population Register comprised the control group. Prognostic factors MPN subtype (polycythemia vera, essential thrombocythemia, or primary myelofibrosis), age at MPN diagnosis, sex, and calendar period of MPN diagnosis. Outcomes Outcomes were nonfatal and fatal arterial thrombosis (myocardial infarction, ischemic stroke, or peripheral arterial thromboembolism) and venous thrombosis (pulmonary embolism, deep venous thrombosis, abdominal venous thrombosis, cerebral venous sinus thrombosis, or other venous thromboembolism) 30 days after diagnosis of MPN. Main results Risks for overall, arterial, and venous thrombosis were increased at 3 months, 1 year, and 5 years and were higher closer to time of diagnosis (Table). Conclusion Patients with myeloproliferative neoplasms had increased risk for arterial and venous thrombosis, especially soon after diagnosis. Risk for arterial and venous thrombosis in patients with myeloproliferative neoplasms* Outcomes Time since diagnosis Hazard ratio (95% CI) All thrombosis 3 mo 4.0 (3.6 to 4.4) 1 y 2.4 (2.3 to 2.6) 5 y 1.8 (1.6 to 1.9) Arterial thrombosis 3 mo 3.0 (2.7 to 3.4) 1 y 2.0 (1.8 to 2.2) 5 y 1.5 (1.4 to 1.6) Venous thrombosis 3 mo 9.7 (7.8 to 12.0) 1 y 4.7 (4.0 to 5.4) 5 y 3.2 (2.9 to 3.6) *CI defined in Glossary. Adjusted for age at MPN diagnosis, sex, and calendar period of MPN diagnosis. Myocardial infarction, ischemic stroke, or peripheral arterial thromboembolism. Pulmonary embolism, deep venous thrombosis, abdominal venous thrombosis, cerebral venous sinus thrombosis, or other venous thromboembolism. Commentary A previous study showed an increased risk for thrombosis in 33% of patients with MPNs, most of which occurred around the time of MPN diagnosis (1). The study by Hultcrantz and colleagues confirms findings of other population-based studies; specifically, patients with MPM have a high rate of thrombosis, the incidence of thrombosis is highest around the time of diagnosis, and thromboses are both arterial and venous. What is unique is that they reported risk for thrombosis longitudinally compared with a control population at 3 months, 1 year, and 5 years after diagnosis and reported a decrease in thrombotic risk in years 1 and 5 compared with 3 months. The study also reported decreased risk for venous thrombosis by year 1 and 5 in patients diagnosed after 1999 compared with those diagnosed earlier. However, this trend was not seen in patients with arterial thrombosis. This may suggest that prevention of arterial disease has not changed much over this period, whereas prevention of venous thrombosis has improved. As with most epidemiologic studies, these findings probably won't change clinician practice. However, they do reinforce the high rate of thrombosis around the time of diagnosis (odds ratios for arterial and venous thrombosis within 30 d before or after MPN diagnosis was 15.6 and 29.5, respectively) and may encourage investigation of interventions to decrease the rate of thrombosis during this critical time. This may be challenging because many patients with MPNs present with a thrombotic event. A study that focuses on patients with MPN who do not present with thrombosis and compares an anticoagulant plus aspirin with aspirin alone for a short time after diagnosis, with all patients continuing aspirin long-term, could be informative.