When should anti-thrombotic therapy be given to myelofibrosis patients at high risk of thrombosis?

Anti-Thrombotic Therapy in Myelofibrosis Patients

All myelofibrosis patients without contraindications should receive low-dose aspirin (81-100 mg daily) as baseline anti-thrombotic therapy, with escalation to full anticoagulation only when active thrombosis occurs. 1

Baseline Anti-Thrombotic Strategy

Universal Aspirin Therapy

• Low-dose aspirin (81-100 mg daily) is recommended for all myelofibrosis patients to reduce thrombotic risk, which occurs in approximately 9.5% of newly diagnosed patients. 2, 1
• This recommendation applies regardless of age or prior thrombotic history, provided no contraindications exist. 1

Critical Pre-Treatment Assessment

• Screen for acquired von Willebrand disease before initiating aspirin in patients with platelet counts >1,500 × 10⁹/L, as extreme thrombocytosis paradoxically increases bleeding risk. 1, 3
• Perform coagulation testing in patients with elevated platelet counts, splenomegaly, or unexplained bleeding before starting antiplatelet therapy. 1

Escalation to Full Anticoagulation

Indication: Active Thrombosis Only

• Full-dose anticoagulation (LMWH, DOACs, or warfarin) should be initiated only when active thrombosis occurs, not for primary prevention in myelofibrosis. 1
• The choice of anticoagulant agent follows standard thrombosis management guidelines based on the type and location of thrombotic event. 1

Combination Strategy for Active Thrombosis

• When thrombosis occurs, combine full anticoagulation with cytoreductive therapy (hydroxyurea for older patients, interferons for younger patients or those of childbearing age) to control myeloproliferation and reduce recurrent thrombotic risk. 1, 4
• This dual approach provides the lowest recurrence risk compared to anticoagulation alone. 5

Special Circumstances Requiring Aspirin Modification

Extreme Thrombocytosis with Bleeding

• Immediately withhold aspirin if bleeding occurs in patients with platelet counts >1,500 × 10⁹/L until bleeding is controlled. 1
• Initiate cytoreductive therapy to normalize platelet counts before restarting aspirin. 1

Perioperative Management

• Coordinate with surgical teams regarding aspirin continuation or interruption based on bleeding versus thrombotic risk assessment. 1
• Mandatory coagulation testing for acquired von Willebrand disease before high-risk surgical procedures in patients with elevated platelet counts or splenomegaly. 1

Monitoring Requirements

Regular Surveillance (Every 3-6 Months)

• Assess for new thrombotic or bleeding events at each visit. 1, 4
• Monitor complete blood counts to track platelet trends, as both extremes (>1,500 × 10⁹/L or thrombocytopenia) alter bleeding/thrombotic risk. 1
• Evaluate splenomegaly progression, which correlates with coagulopathy risk. 1

Key Clinical Pitfalls

Avoid Prophylactic Anticoagulation

Unlike myeloma patients receiving immunomodulatory drugs who may warrant prophylactic LMWH or DOACs based on risk scores 2, myelofibrosis patients should not receive prophylactic full-dose anticoagulation—only aspirin for primary prevention. 1

Distinguish from Other Myeloproliferative Neoplasms

While polycythemia vera and essential thrombocythemia patients may require cytoreductive therapy based on age >60 years or prior thrombosis 2, 4, myelofibrosis has a lower baseline thrombotic risk (9.5% vs 28.6% in PV and 20.7% in ET) 2, making universal cytoreduction for thrombosis prevention less clearly indicated.

Manage Cardiovascular Risk Factors Aggressively

Hypertension, diabetes, hyperlipidemia, and tobacco use significantly amplify thrombotic risk in myeloproliferative neoplasms 4, 6, making their control essential alongside aspirin therapy.