A blood clot is a serious condition that needs treatment right away. People with cancer and those receiving cancer treatment have an increased risk for blood clots.
Normal blood clotting, called coagulation, is a complex process. It involves specialized blood cells, called platelets, and different proteins in the blood, called clotting or coagulation factors. These platelets and coagulation factors clump together to heal broken blood vessels and control bleeding. Coagulation factors that promote bleeding and those that promote clotting must be balanced.
Blood clotting disorders occur when some clotting factors are missing or damaged. This causes clots to form inside the body that block normal blood flow and cause serious problems.
Blood clots can occur in and travel to different parts of the body, including:
Veins, called a venous thromboembolism (VTE). If the vein is in the leg, thigh, or pelvis, it is called deep venous thrombosis (DVT).
The lungs, called a pulmonary embolism (PE).
An artery. This is less common but also very serious.
Signs and symptoms of clotting problems
People with clotting problems may experience:
Arm or leg swelling on 1 side of the body
Pain in the arm or leg where a blood clot is located
Trouble breathing or chest pain when breathing
Rapid heart beat
Low oxygen levels
Relieving side effects is an important part of cancer care and treatment. This is called palliative care or supportive care. Tell your health care team about any of these symptoms immediately. Even people with low levels of platelets can develop a blood clot. Sometimes people do not know they have a blood clot until it is diagnosed during a test.
Causes of clotting problems
People with cancer have a higher risk of blood clots and clotting disorders. This may be caused by the cancer or its treatment. Such risk factors include:
Cancers of the lung, kidney, brain, digestive system, female reproductive system such as uterine cancer, and blood such as leukemia and lymphoma
Metastatic cancer, which is cancer that has spread to other parts of the body from where it started
Cancer treatment, including surgery lasting longer than 1 hour, chemotherapy, radiation therapy, and hormone therapy. Drugs called anti-angiogenic drugs that block the formation of new blood vessels such as thalidomide (Synovir, Thalomid) and lenalidomide (Revlimid) may also raise the risk of blood clots.
Treatment with drugs called erythropoiesis stimulating agents that help the body make more red blood cells, such as epoetin (Epogen, Eprex, Procrit) and darbepoetin (Aranesp)
Long-term use of an intravenous catheter or port
Blood clots can also be caused by reasons other than cancer and its treatment, such as:
Long periods of inactivity, such as a long plane or car ride. This may also include being in the hospital, because most people in the hospital cannot be physically active and need to stay in bed or are unable to get out of bed.
Having other diseases or conditions in addition to cancer, such as obesity, infection, kidney disease, lung disease, or a blood clot in a blood vessel called an artery that carries blood away from the heart.
Race/ethnicity. The risk is higher for black people and lower for white and Asian people.
A condition that is inherited, meaning it is passed down from parent to child in a family. This includes a factor V Leiden mutation, which is a condition that causes too much blood clotting.
Diagnosing clotting problems
Your doctor may use one or more ways to find a blood clot, including:
A Doppler ultrasound. An ultrasound uses sound waves to look at the flow of blood in veins in the arms or legs. It can detect decreased blood flow from a blood clot.
A computed tomography (CT) scan. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A special dye called a contrast medium is injected into a patient’s vein or given as a pill or liquid to swallow before the scan to provide better detail on the image. Doctors commonly use CT scans to diagnose a blood clot in the lungs or a PE.
A lung ventilation/perfusion (VQ). This test that can diagnose a PE is made up of 2 different parts:
An angiogram. This test can detect a blood clot in an artery. During an angiogram, a dye is injected into the artery. And then the artery is examined with a special x-ray device called a fluoroscope.
Preventing and treating clotting problems
Blood clots can be prevented and treated with drugs. Anticoagulants are drugs that stop clots from happening or stop existing clots from getting worse. These drugs may increase a person’s risk of bleeding, but they are safe for most people. Typical anticoagulants include:
Some of these drugs are taken by mouth. Others are given as an injection under the skin, called a subcutaneous injection.
The American Society of Clinical Oncology (ASCO) recommends the following to help prevent blood clots in people with cancer:
Some people staying in the hospital may need to take medicine to prevent blood clots. This type of medicine is called an anticoagulant. Whether someone needs to take an anticoagulant may depend on how long their hospital stay is and whether they are at a high risk of blood clots.
People with multiple myeloma who are taking an anti-angiogenic along with chemotherapy and/or dexamethasone (multiple brand names) should take heparin or low doses of aspirin.
People who will be having a major cancer surgery should receive treatment to prevent blood clots after surgery. Treatment should continue for at least 7 to 10 days or up to 4 weeks, depending on the type of surgery and your risk of blood clots.
People who have a high risk of blood clots but are not staying in the hospital may receive apixaban, rivaroxaban, or some form of heparin
Your doctor may also recommend the following methods in addition to taking medicine to prevent blood clots:
Graduated compression stockings, which are a type of support hose
Intermittent pneumatic compression, which squeezes the legs through a sleeve connected to a machine
Mechanical foot pumps
Learn more about these recommendations on a separate ASCO website.
A person with a blood clot needs treatment right away. The most common treatment is an anticoagulant that can be injected under the skin or into a vein. But some people may take a pill that is swallowed. Once the blood is considered thin enough, there is a lower risk of clotting.
People who are receiving blood thinners must be regularly monitored for any increased bleeding. Some people are unable to receive blood thinners because they have low platelet levels or a high risk of bleeding. For these people, a special type of filter can be placed in the body to prevent a blood clot from traveling to the lungs, a condition that can be very dangerous.
Questions to ask the health care team
Talk with your health care team to learn more about your risk of developing a blood clot, how blood clot prevention will be included in your overall treatment plan, and what treatments are available if you develop a blood clot.
Consider asking the following questions:
Do I have a higher risk of a blood clot?
What can be done to prevent a blood clot before it starts?
What are the signs and symptoms of a blood clot?
If I have a blood clot or have had them before, what treatment do you recommend?
How long will I need this treatment?
What is my risk of bleeding with such treatment? Are there other side effects?
What health conditions or medications may interfere with the treatment for blood clots?
Who should I call if I have concerns about a symptom?
When to Call the Doctor During Cancer Treatment