Increased Risk of Thrombosis in Cancer Patients

Cancer patients are at a higher risk of developing a type of blood clot known as deep vein thrombosis (DVT). If you have cancer, you are at a higher risk of getting deep vein thrombosis, and if you have deep vein thrombosis, you also have a much higher chance of getting diagnosed with cancer. Read to find out about the increased risk of thrombosis in cancer patients.

The association between cancer and thrombosis was first reported in 1865 by Armand Trousseau. Since then, there have been many studies that have clearly established that thrombosis is a common complication in cancer patients. Thrombosis is, in fact, the second leading cause of mortality in cancer patients.^{(1, 2)}

Thrombosis-related complications in cancer patients can range from venous or arterial thromboembolism to disseminated intravascular coagulation. The most common type of thrombosis in cancer patients is known as venous thromboembolism (VTE).^{(3, 4)} There are many risk factors for why some cancer patients develop VTE, including immobilization and chemotherapy. These cancer-associated factors increase the risk of cancer patients developing venous thromboembolism as compared to non-cancer patients.

At the same time, cancer cells are also capable of activating the coagulation cascade and other prothrombotic properties of host cells, and several anti-cancer treatments are known to act as a mechanism for increasing the risk of developing venous thromboembolism. However, despite this association between cancer and thrombosis being well known, the exact mechanism that causes thromboembolic cases in cancer patients is not really clear, and there might be several reasons behind such a development.⁽⁵⁾

1. Venous Thromboembolism (VTE)

   As mentioned above, venous thromboembolism is the most common type of thrombosis seen in cancer patients. venous thromboembolism comprises of deep vein thrombosis (DVT) and pulmonary embolism (PE). As the name suggests, DVT develops deep in the veins, most commonly in the legs. It is possible to get one in the arm as well sometimes. In case the DVT is in the arm, it is known as upper-extremity DVT, and it can cut off the blood flow to the arm. DVTs cause pain, swelling, redness, and the skin near the blocked vein may feel warm to the touch.^{(6, 7, 8)}

   A pulmonary embolism (PE) is more severe than a DVT. This happens when a DVT breaks free and travels to the lungs. A pulmonary embolism is a life-threatening emergency, and it can make it difficult for a person to breathe while increasing the heart rate, causing chest pain and dizziness. PE can cause a person to lose consciousness.^{(9, 10)}

   There are many causes of venous thromboembolism, but the most common triggers for venous thromboembolism are cancer, surgery, immobilization, and hospitalization.

   DVT usually forms in the legs when some factor causes a change or slow down in the blood flow. In women, pregnancy and the use of hormonal medications like oral contraceptives or estrogen for menopause symptoms can be a cause. There are certain people who are at a higher risk of developing venous thromboembolism, including:

   • Older adults
   • People who are overweight or obese.
   • People with cancer or other medical conditions, such as autoimmune disorders like lupus.
   • People whose blood is thicker than normal as their bone marrow is producing excessive blood cells.

   While any person is at a risk for developing a venous thromboembolism or a blood clot, having cancer and some of the cancer treatments increase the risk for developing a blood clot or VTE. It is estimated that nearly 4 to 20 percent of cancer patients will experience venous thromboembolism at some stage of their illness. This rate is the highest in the initial days after the diagnosis. Every year, 0.5 percent of cancer patients are estimated to experience thrombosis as compared to the 0.1 percent incidence rate in the non-cancerous general population.⁽¹¹⁾

   It has been seen that a diagnosis of venous thromboembolism is a severe complication of cancer that tends to negatively impact the patient’s quality of life and also decrease the overall survival rate.^{(12, 13)} Those who develop a blood clot soon after being diagnosed with cancer or within the year that follows also tend to have a dramatically worse prognosis as compared to cancer patients who do not have VTE.⁽¹⁴⁾

2. Arterial Thrombosis

   There is a lot less data available on the risk of cancer and arterial thrombosis as compared to that on venous thromboembolism and cancer. Nevertheless, arterial thrombosis is also observed in cancer patients. Arterial thrombosis develops when a blood clot forms in an artery. Arteries are blood vessels that transport blood away from the heart to the organs. Arterial thrombosis is very similar to DVT, just that it affects the arteries and not the veins. Arteries are larger and carry more blood. Arterial thrombosis can also cause life-threatening events, such as a stroke or heart attack.^{(15, 16, 17)}

   According to a study carried out by Navi et al., the incidence rate of arterial thrombosis at six months was 4.7 percent in cancer patients as compared to the 2.2 percent in the control participants.⁽¹⁸⁾

   While anyone can develop arterial thrombosis, some people are at a higher risk. The most likely cause of arterial thrombosis is usually damage to the artery due to atherosclerosis. Atherosclerosis happens over a period of time as there is a buildup of plaque on the walls of the arteries. This causes the arteries to narrow and harden, increasing the risk of developing arterial thrombosis.^{(19, 20)}

Some cancers actually pose a higher risk of developing blood clots, especially cancers of the pancreas, stomach, uterus, lungs, kidneys, and ovaries. Even some blood cancers like lymphoma and myeloma also increase the risk. The treatments for these cancers, which involve surgery, hospitalization, chemotherapy, hormonal therapy, and catheters to administer the treatment, are also known to increase the risk of developing venous thromboembolism.^{(21, 22)}

There are many other factors that also increase the risk for a venous thromboembolism in people being treated for cancer. These include:

• Having developed a blood clot earlier.
• Having a family history of blood clots or some inherited clotting disorders.
• Hospitalization for major surgery or illness, especially those that involve the abdomen, knee, hip, or pelvis.
• Having severe muscle injury or broken bone.
• Severe physical trauma, such as a car accident.
• Having a serious medical condition, such as heart and lung diseases or diabetes.
• Remaining seated for too long, such as when traveling for more than four hours, especially while keeping your legs crossed.
• Other causes of immobility such as extended bed rest.
• Being obese or overweight.
• Smoking

Treatment is critical in the fight against cancer. However, the same treatment may also increase the risk of the formation of blood clots. Chemotherapy, a common type of cancer treatment that uses one or more medications in combination, and surgery can cause damage to the walls of your blood vessels and impact the manner in which they function. This can also cause a blood clot either in your veins or arteries. When chemotherapy kills the cancer cells, certain substances that cause clotting also get released into your bloodstream.

Some types of chemotherapy medicines are less likely to promote the formation of blood clots than others, and it is a good idea to ask your doctor about this if there is a history of blood clots in your family or if you already know that you are at a higher risk of developing thrombosis.

Some examples of drugs that damage the blood vessels or reduce the level of unique proteins in the blood to stop clotting include:

• Thalidomide (brand name: Synovir, Thalomid)
• Darbepoetin (brand name: Aranesp)
• Lenalidomide (brand name: Revlimid)
• Epoetin (brand name: Epogen, Procrit)
• Tamoxifen (brand name: Nolvadex, Soltamax) – this a hormone usually used in the treatment of breast cancer

The risk of getting DVT from your cancer treatment can also go up in the following instances:

• If you have had cancer surgery, especially around the hips or abdomen.
• If you continue to lie in bed as you recover and do not move around much.
• You get a central venous catheter inserted in your chest or arm frequently while in the hospital. This is a tube that is used to administer medicines.

Of course, keep in mind that your doctor will carefully weigh all the pros and cons of each treatment and medication before they suggest you any form of treatment for your cancer.

If you are concerned about your risk of DVT and you want to reduce this risk, your first approach should be to discuss the same with your doctor. The exact risk of thrombosis also depends on several factors, such as the type of cancer you have, the treatment you require, your overall health, and whether you are staying in the hospital or at home. If you are at a high risk of developing a blood clot, your doctor is likely to put you on medications known as blood thinners or anticoagulants. You should also try to start some level of physical activity as soon as possible after your surgery. Wearing specially designed tight socks, known as compression stockings, can also reduce the risk of blood clots and also improve blood flow.

In case you do develop DVT, your doctor will act swiftly, and you will get treated with a blood thinner. You might have to continue this medication for several months or until the time you become cancer free.

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