Cancer and the Risk of Blood Clots

The risk of developing a blood clot (deep vein thrombosis or DVT) during cancer treatment is very real but often overlooked. The public became more aware of DVTs when TV journalist David Bloom died from a pulmonary embolism while reporting from Iraq, but there is still too little awareness of this common complication of cancer. Knowing what symptoms you should watch for, and things you can do to lower your risk, can go a long way in reducing the chance that this serious complication will interfere with your cancer treatment.

Blood Clots
Blood Clots

What Are Blood Clots (DVTs)?

A DVT is a blood clot that forms in a deep vein in the body, usually in the legs. If the clot breaks loose, it can travel to the lungs and cause a blockage in the arteries leading to the lungs, a condition known as pulmonary embolism.

How Common Are Blood Clots (DVTs) With Lung Cancer?

Between 3% and 15% of people with lung cancer develop blood clots during their treatment, according to various studies. They are more common in those with non-small cell lung cancer than with small cell lung cancer, and individuals with adenocarcinoma appear to be at the greatest risk. Other factors that increase risk include having an advanced stage of lung cancer (for example stage 4 or metastatic disease), or receiving chemotherapy, especially some of the targeted therapies, or post-surgery. Roughly 7% of people that have lung cancer surgery will develop a blood clot.

The Importance of Recognizing Blood Clots (DVTs)

It is very important to be on the lookout for blood clots, since they can lower survival with lung cancer.

In one study, patients with non-small cell lung cancer had a 1.7 fold increased risk of dying if they had a DVT. Another study found that lung cancer patients who had at least one DVT, survived only half as long as those without a DVT. The most dreaded complication of blood clots is that they will break off and travel to the lungs, an emergency situation known as pulmonary embolism, which can be fatal if untreated. Even for clots that do not break loose, you can develop chronic leg pain in the future if they are not treated, something known as post-thrombotic syndrome. Your doctor will check your legs when you are hospitalized, especially after surgery, but the peak incidence of clots following surgery is 7 days afterward – a time when many people may be back home recovering.

Situations That Raise the Risk

Having lung cancer alone increases the risk of developing blood clots, but some situations increase the risk further. Some of these include:

  • Surgery – Especially lung cancer surgery
  • Chemotherapy and some targeted therapies
  • Inactivity or prolonged bed rest
  • Other lung diseases such as COPD
  • Smoking
  • Travel – Extended travel by car or plane increases the risk of blood clots. This can be a concern for those who need to travel long distances for treatment


You need to watch for two types of symptoms: Those that are due to a clot in your leg, or those that might suggest a clot has traveled to your lungs (pulmonary embolism).

Symptoms of blood clots (DVT):

  • None – Occasionally a blood clot is present without any symptoms
  • Leg/calf pain – Especially a cramping type of pain in only one leg
  • Swelling
  • Redness
  • Warmth
  • Pain with extension of your toes – Pain due to a blood clot usually increases if you point your toes toward your head

Symptoms of pulmonary embolism:

  • Chest pain – The chest pain associated with a pulmonary embolism is usually worse with coughing and taking a deep breath
  • Abrupt onset shortness of breath
  • Lightheadedness or fainting
  • Coughing up blood (hemoptysis) – It is very important to be aware of this symptom, since lung cancer itself may cause you to cough up blood

When to Alert Your Doctor

Any of the above symptoms should prompt you to call your physician right away. A pulmonary embolism can be fatal, and you should call 911 immediately if you have any symptoms that might suggest you have a pulmonary embolism.

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