4 Bleeding and Clotting Essentials for Cancer Patients

Depiction of blood clot, as would be seen using scanning electron microscopy..

Having cancer in general -- and having leukemia or lymphoma, in particular -- increases a person’s risk for blood clots and bleeding. This increased risk has to do with the body’s coagulation mechanisms, the effects of cancer and its treatment.

Clotting and Bleeding in Cancer

Blood clots are common in patients with cancer. Clotting, or thromboembolism, may develop because of a prior condition, the cancer itself or as a side effect of treatment.

Likewise, when a person with cancer develops bleeding, doctors have to figure out if the bleeding is from a prior condition, from the malignancy itself, or from the cancer treatments.

1. Cancer May Cause Clotting

Cancer, itself, is a risk factor for clotting. Certain cancers are more strongly associated with clotting, including cancers of the lung, kidney, brain, digestive system, female reproductive system, and the hematologic malignancies, or blood cancers, such as leukemia and lymphoma. The fact that older age is a risk factor for clotting may also be in play, since many cancers tend to develop later in life.

2. Cancer Treatments May Cause Clotting

Surgeries lasting longer than one hour, chemotherapy, radiation therapy and hormone therapy may all increase the risk of blood clots. Certain agents such as thalidomide (Synovir, Thalomid) and lenalidomide (Revlimid) are considered immunomodulatory drugs and they may lead to an increased risk of blood clots.

Other drugs such as bevacizumab (Avastin) block the growth of new blood vessels that feed tumors and are also associated with blood clots.

When a person needs to avoid transfusions, or when a more gradual improvement of anemia is sufficient, erythropoiesis stimulating agents, or ESAs, may be given such as epoetin (Epogen, Eprex, Procrit) and darbepoetin (Aranesp).

These agents are effective, however they are also associated with an increased risk of clotting.

Finally, prolonged immobilization, like what can happen when a person is admitted to the hospital, increases the risk of clotting. This is one of the reasons health care teams try to get hospitalized patients up and walking whenever possible.

3. Cancer May Cause Bleeding

A deficiency in platelets known as thrombocytopenia is a big cause of bleeding in cancer patients. Platelets are those little, sticky packages of cellular material in the bloodstream that clump together to form plugs and stop the bleeding. Thrombocytopenia has many potential causes, and one of them is infiltration of the bone marrow by a malignancy. Patients with leukemia, for instance, may be at increased risk for bleeding when the unhealthy cancer cells infiltrate the bone marrow and essentially take over; they crowd out the normal marrow cells that form the blood—including megakaryocytes, the cells that make platelets.

Another big cause of bleeding in someone with cancer has to do with the characteristics of the malignant tissue.

Some tumors are said to be friable, meaning they break apart very easily and are easily damaged. When the tissue is friable and highly vascular, rich in blood vessels, this is a combination that makes for increased risk of bleeding.

Something called disseminated intravascular coagulopathy, or DIC, refers is basically an imbalance in clotting and bleeding; there is sometimes only clotting present, but there can be both clotting and bleeding. DIC is explained in greater depth in number 4, below, since treatment-associated infection can cause DIC; however, in the case of acute promyelocytic leukemia, or APL, the cancerous cells actually secrete a substance into the bloodstream that initiates the clotting mechanism, causing DIC. About 85 percent of patients diagnosed with APL will develop DIC and bleeding.

4. Cancer Treatments May Cause Bleeding

Many cancer treatments increase the risk of bleeding. Platelets are made from those specialized cells within the bone marrow called megakaryocytes, and chemotherapy that suppresses the bone marrow -- so-called myelosuppressive agents -- can also suppress the formation of platelets, increasing the risk for bleeding. Radiation and bone marrow transplantation may contribute to thrombocytopenia and bleeding risk as well.

Suppression of the bone marrow during treatment may also predispose a person to bacterial blood stream infection, or sepsis. When sepsis occurs, it can trigger disseminated intravascular coagulation. In cases of DIC, there can be bleeding as platelets and factors needed for coagulation are consumed by a massive abnormal clotting reaction. Widespread clotting essentially uses up the materials needed for clotting, which can result in bleeding elsewhere. In some cases, DIC may be what causes a person with cancer to become diagnosed in the first place. Acute promyelocytic leukemia is one such cancer that is strongly associated with DIC.


National Comprehensive Cancer Network. Chemotherapy–induced anemia. NCCN Guidelines version 1.2016.

Martin, E. Concise Medical Dictionary. Oxford University Press, 2015.

Escobar M. Bleeding in the patient with a malignancy. Cancer. 2012;118(2):312-320.

Cuker A. Toxicities of the thrombopoietic growth factors. Semin Hematol. 2010;47(3):289-298.

Cancer.net. Preventing and Treating Blood Clots. Accessed September 2015.

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