Breast Cancer and Blood Clots: What’s the Connection?

Many people with cancer may not be aware of their risk for blood clots, especially during treatment. Blood clots may be referred to as venous thromboembolism (VTE). VTE includes both deep vein thrombosis (DVT) and pulmonary embolism (PE). A DVT occurs when a blood clot forms in a deep vein, usually in the lower leg, thigh, or pelvis. A PE occurs when a clot breaks loose and travels through the bloodstream to the lung.1 A PE can be fatal, so it’s crucial to be aware of your risk for developing clots, as well as signs and symptoms of blood clots.

Who is at risk for a blood clot?

People with breast cancer are 3.5 times more likely to develop VTE compared to people without cancer.2 Other factors that can increase the risk for women with breast cancer are included below. (Please note that many research studies on VTE and breast cancer have only included women.)

  • Chemotherapy treatment - VTE risk for those currently undergoing chemotherapy is about 10 times higher than those not receiving chemotherapy. This risk continues for about one month after stopping treatment.
  • Tamoxifen treatment - Compared to before starting tamoxifen, the risk for VTE is 5 times higher while taking tamoxifen. Researchers have found that this risk to be highest in the first three months of starting the medication.
  • After surgery - The risk for VTE was observed to be 2 times higher for women who had breast surgery. This increased risk continues for about one month after surgery.
  • Metastatic breast cancer - Risk of VTE for people with cancer is increased for those with metastatic, or stage IV, cancers. This risk has been observed in people with many different types of cancer.
  • Age at diagnosis - While older age is a risk factor for VTE even in those without cancer, the risk for VTE is increased for those diagnosed with breast cancer at an older age.
  • Higher BMI - As for those without cancer, there is increased risk of VTE associated with a higher BMI and in those with obesity.2
  • Central venous catheter use - Those using a central venous catheter, sometimes known as a central line or a chemo port, are at an increased risk for VTE compared to those without a catheter.1

In addition to breast cancer-related risks, general risk factors for developing blood clots include being immobile for long periods of time, pregnancy or recently giving birth, family history, genetics, and other health conditions.1

What are the symptoms of blood clots?

Many clots begin as a DVT. These are clots formed typically in the legs or major veins of the body. Pain in your calf, swelling/redness of one leg, sudden shortness of breath, and chest pain can all be signs of a DVT.3 It's important to recognize these signs and symptoms in order to seek the help you may need before a clot can travel to other parts of the body.

How can someone reduce their risk of a blood clot?

Besides paying attention to the potential warning signs, you can also take steps to reduce your clot risk, especially during treatment. By moving around more and limiting the time you are immobile, like when in the hospital or on long trips, you can decrease your risk significantly. Additionally, it is important to discuss any potential risk factors for VTE and what you can do to prevent clotting with your doctor.

Some doctors may prescribe blood thinners to help prevent your blood from clotting. Blood thinners, also called anticoagulants, are often prescribed to people after major surgeries, when they may be recovering and unable to move around, but can be used at any time. These medications can also come with risks, such as an increased risk of bleeding.3 It is recommended to discuss the benefits and risks of blood thinners, along with your personal risk for blood clots, when making treatment decisions with your healthcare team.

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