Cancer and some treatments for cancer may cause changes to your blood that can encourage the formation of blood clots. Having cancer can greatly increase your risk of a pulmonary embolism.
A pulmonary embolism (PE) is when a blood clot or another foreign substance blocks an artery in your lungs. It’s a life threatening medical emergency, and is the second leading cause of death in people with cancer, behind cancer itself.
A PE is typically caused by a deep vein thrombosis (DVT) that travels from your leg to your lungs. DVT is a blood clot in one of your deep blood vessels.
Both cancer itself and some cancer treatments may increase your risk of developing blood clots.
Learn more about the link between PE and cancer, including what types of cancer are associated with PE, how cancer increases your risk, and how PE is managed.
The main reason cancer increases your risk is that it may make your body more prone to blood clots.
People with cancer often have blood that’s “stickier” than usual due to the release of chemicals by cancer cells that stimulate your blood to produce more clotting factors. Clotting factors are proteins made by your liver that help you stop bleeding when they contact blood cells called platelets.
Cancer is estimated to increase the risk of venous thromboembolism four to seven times. Venous thromboembolism refers to blood clots in veins, including DVT, that can cause PE.
Some cancer treatments can also make you more prone to blood clots. For example, chemotherapy drugs linked to blood clots include:
Other causes
PE isn’t always caused by a blood clot. A rare cause is tumor embolism, where fragments of a tumor break off and clog one of your arteries. Other potential causes may include:
- Central venous catheter thrombosis: Where a blood clot forms around a central catheter.
- Tumor invasion: Where a tumor grows into your blood vessel, potentially causing an obstruction.
Some types of cancer may put you at a particularly higher risk of PE. According to Cancer Research UK, these may include:
Having metastatic cancer, meaning your cancer has spread to distant tissues, is also considered a risk factor for PE.
Some risk factors for PE in people with cancer may include:
- having a high risk type of cancer
- immobility and extended bed rest
- elevated serum D-dimer levels
- obesity
- smoking
- high blood pressure
- low physical activity
Symptoms of PE in people with cancer are similar to those in people without cancer.
However, a greater percentage of people may have no noticeable symptoms. Research suggests that around 31% of people with cancer who experience a PE have no symptoms. This is known as asymptomatic PE.
According to the American Lung Association, the signs and symptoms of PE can include:
- sudden shortness of breath
- sharp chest pain that may worsen when breathing
- lightheadedness
- coughing up blood
- fever
- leg pain, which may be accompanied by swelling, skin discoloration, or warmth
- back pain
- bluish lips or nails, which might be harder to spot on darker skin tones
- excessive sweating
- increased blood pressure
- rapid heart rate
PE is often diagnosed when someone visits the emergency room with symptoms that onset suddenly. Symptoms of PE can be general and difficult to differentiate from other conditions.
A healthcare professional will likely initially:
- ask you about your symptoms
- perform a physical exam, where they inspect your leg for evidence of a blood clot that may have traveled to your lungs
- review your personal and family medical history
According to the American Lung Association, a doctor may order the following tests to help rule out other conditions and confirm the diagnosis:
- CT pulmonary angiogram
- pulmonary V/Q scan to see if your airflow is obstructed
- D-dimer blood tests to look for blood clot formation
- chest X-ray to rule out other conditions
- ultrasound of your leg to measure blood flow and assess for blood clots
- electrocardiogram (ECG) to measure heart activity
- pulmonary angiography to look for blood clots in your lungs
Some PEs may be detected when you receive a CT scan for an unrelated reason, such as for monitoring lung cancer. Finding a PE incidentally is known as unsuspected PE.
The EPIPHANY index
Doctors developed the EPIPHANY index to classify cancer-associated PE into three risk categories based on the odds of developing complications within 15 days.
It’s based on factors such as whether you have a high heart rate, shortness of breath, or other related factors.
Most people with cancer who develop a PE are treated with parenteral anticoagulation medications. These medications are administered through injections or infusions to help break up blood clots. You may also receive medications such as low-molecular-weight heparin or fondaparinux.
After taking these medications, most people are switched to oral anticoagulants for a minimum of 3 months.
Life threatening blood clots may need to be removed with a surgical procedure called embolectomy.
PE can be life threatening. It may cause complications like:
If left untreated, the death rate may be as high as 30% in the general population and up to 8% in people who receive treatment.
PE is the second leading cause of death in people with cancer. Some research also suggests that around 3 in 100 people with cancer experience a PE within 1 year of receiving their cancer diagnosis.
Developing PE comes with a high risk of death. People who have PE are also more likely to develop another embolism compared to people who have never experienced a PE.
It’s important to note, however, that everyone’s outlook will be different. If you have cancer and have experienced a PE, speak with your doctor. They could help you understand how the condition may affect your life expectancy.
Cancer raises the risk of developing PE. People with cancer often have “sticky” blood that can increase their risk of blood clots. Cancer treatments, like some types of chemotherapy and radiation therapy, may also increase your risk.
It’s important to seek immediate medical attention if you believe that you or somebody you’re with experiences a PE. Prompt treatment can help minimize the chances of developing complications that can be life threatening.