Compared with the general population, patients with cancer are at a greater risk of developing venous thromboembolism (VTE) making them vulnerable to increased healthcare costs, morbidity, and death.

New evidence-based guidelines from the American Society of Hematology (ASH) were established to help patients and healthcare professionals in decision making for the prevention and treatment of VTE as about 20% of all cases occur in patients with cancer.

The nearly 3 dozen guidelines address mechanical and pharmacologic prophylaxis in hospitalized patients with cancer, patients undergoing a surgical procedure, and ambulatory patients receiving chemotherapy. In addition, recommendations were also provided for the use of anticoagulation for the initial (within the first week), short-term (3 to 6 months), and long-term (beyond 6 months) treatment of VTE. The authors broke them down into strong recommendations and conditional recommendations.

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One of the strong recommendations includes not using thromboprophylaxis in ambulatory patients receiving chemotherapy at low risk of VTE. Classification of patients as being low-, intermediate-, or high-risk for VTE should be based on a validated risk-assessment tool complemented by clinical judgment and experience. “Even for patients at high risk for thrombosis, thromboprophylaxis should be used with caution in those with a high risk for bleeding,” the authors stated. In addition, they strongly recommended using low-molecular-weight heparin (LMWH) for initial treatment of VTE.

Conditional recommendations are as follows: using thromboprophylaxis in hospitalized patients with cancer, LMWH or fondaparinux for surgical patients with cancer, and LMWH or direct oral anticoagulants (DOACs) in ambulatory patients with cancer receiving systemic therapy at high risk of VTE.

Looking at the treatment timeframe, the authors advised using LMWH or DOACs for initial treatment of VTE, DOACs for the short-term treatment of VTE, and LMWH or DOACs for the long-term treatment of VTE in patients with cancer as conditional recommendations.

“When engaging in shared decision-making, it is important to recognize that, for most patients, the diagnosis of cancer takes primacy over their VTE,” the authors said. But referring to these guidelines can help meet patients’ needs.

The guidelines were made using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. These guidelines are not intended to serve or be construed as a standard of care,” the authors wrote. “Clinicians must make decisions on the basis of the clinical presentation of each individual patient, ideally through a shared decision-making process that considers the patient’s values and preferences with respect to the anticipated outcomes of the chosen option.” 

Disclosure: All authors were members of the guideline panel, the systematic review team, or both; all completed disclosure forms that were reviewed by ASH. Please refer to the original article for a complete list of disclosures.


Lyman GH, Carrier M, Ay C, et al. American Society of Hematology 2021 guidelines for management of venous thromboembolism: prevention and treatment in patients with cancer. Blood Advances. 2021;5(4):927-974. doi:10.1182/bloodadvances.2020003442