High rate orf recurrent venous thromboembolism in patients with myeloproliferative neoplasms and effect of prophylaxis with vitamin K antagonists

The optimal duration of treatment with vitamin K antagonists (VKA) after venous thromboembolism (VTE) in patients with Philadelphianegative myeloproliferative neoplasms (MPNs) is uncertain. To tackle this issue, we retrospectively studied 206 patients with MPNrelated VTE (deep venous thrombosis of the legs and/or pulmonary embolism). After this index event, we recorded over 695 pt-years 45 recurrences, venous in 36 cases, with an incidence rate (IR) of 6.5 per 100 pt-years (95% confidence interval (CI): 4.9–8.6). One hundred fifty-five patients received VKA; the IR of recurrent thrombosis per 100 pt-years was 4.7 (95% CI: 2.8–7.3) on VKA and 8.9 (95% CI: 5.7–13.2) off VKA (P = 0.03). In patients receiving VKA, the IR of recurrent thrombosis per 100 pt-years was 5.3 (95% CI: 3.2–8.4) among 108 patients on long-term VKA and 12.8 (95% CI: 7.3–20.7) after discontinuation among the 47 who ceased treatment (P = 0.008), with a doubled risk of recurrence after stopping VKA (hazard ratio: 2.21, 95% CI: 1.19–5.30). The IR of major bleeding per 100 pt-years was 2.4 (95%: CI: 1.1–4.5) on VKA and 0.7 (95% CI: 0.08–2.5) off VKA (P = 0.08). In conclusion, in MPN patients with VTE recurrent thrombosis is significantly reduced by VKA and caution should be adopted in discontinuation; however, the incidence of recurrence on treatment remains high, calling for clinical trials aimed to improve prophylaxis in this setting.