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Prevention of VTE after initial presentation and cancer treatment


KEY POINTS

  • In patients with cancer with venous thromboembolism (VTE), the risk of VTE recurrence is increased six-fold with an annual rate as high as 30% in the absence of anticoagulation and as high as 20% even within the initial 6 months on anticoagulation therapy.

  • The majority of VTEs occur within the first months of cancer diagnosis.

  • Several additional risk score tools have been developed that expand the timeframe of prediction from 2.5 (Khorana score) to 6 months, but await external validation and assessment of suitability for long-term prediction in survivorship.

  • The rate of VTE recurrence differs significantly by cancer type, stage of disease, and stage progression over time; specific risk factors include brain, lung, pancreatic, or ovarian cancer; myeloproliferative or myelodysplastic disorders; stage IV cancer; cancer stage progression; or leg paresis.

  • If outlined risk factors are present, it is likely best to continue anticoagulation (premature discontinuation of anticoagulation should be avoided).

  • The original and modified Ottawa prediction scores were developed to risk stratify for recurrent VTE; among the variables included in the score, female gender and lung cancer increase the risk, whereas breast cancer and stage I (/II) decrease the risk.

  • The risk for VTE remains increased in cancer survivors, especially in childhood cancer survivors who face a 25-fold higher risk than their siblings without disease.

Introduction

Cancer accounts for up to 20% of venous thromboembolic events occurring in the community, increasing the risk of venous thromboembolism (VTE) by a factor of 4 (without chemotherapy) to 7 (with chemotherapy). The likelihood of developing VTE is highest during the first 3 months after the cancer diagnosis and the majority of thrombotic events occur within the first year. For patients with cancer-associated VTE, approximately half have metastatic disease at the time of VTE diagnosis. With nearly 2 million Americans given a new cancer diagnosis each year and an estimated nearly 20 million cancer survivors in the United States alone, there is a large burden of potential cancer-related VTE to manage.

This topic gains further significance based on the fact that thromboembolic events, including VTE, are a leading cause of death among cancer outpatients; patients with cancer with VTE have a 3-fold and 8-fold higher risk of death than patients with cancer but no VTE and patients with VTE but no cancer, respectively. Those surviving face a high risk of VTE recurrence, as high as 30% annually in the absence of anticoagulation therapy and as high as 20% after 6 months on therapy. This chapter focuses on this risk of recurrent VTE in patients with active cancer and the risk of VTE in cancer survivors. Management of acute VTE is covered in Chapter 18 .

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