Cancer and its treatment significantly increase the risk of blood clots, a complication that affects about one in five clot cases, according to the Centers for Disease Control and Prevention. Patients undergoing chemotherapy face even greater danger—roughly one in ten develop a clot at some point during their treatment.
Several factors explain the connection between cancer and blood clots. Cancer cells produce substances like tissue factor and cancer procoagulant, which promote clotting. Some tumors release inflammatory cytokines, making blood more prone to clotting, while others damage blood vessel walls, disrupting normal flow.
Chemotherapy worsens the problem. Drugs like cisplatin, doxorubicin, and gemcitabine harm blood vessels and cause inflammation, raising clot risk. Radiation, hormonal therapies such as tamoxifen, and immunotherapies also contribute. Venous catheters, frequently used in cancer care, can irritate blood vessel linings and increase risk.
Prolonged inactivity during treatment adds to the danger. Patients bedbound after chemotherapy are more likely to develop clots due to stagnant blood flow.
Blood clots appear differently depending on their location. Deep vein thrombosis (DVT), which occurs in the arms or legs, often causes swelling, pain, redness, and warmth in the affected area. If a clot breaks loose and travels to the lungs, it becomes a pulmonary embolism (PE)—a medical emergency with symptoms like sudden shortness of breath, chest pain that worsens with deep breaths, and a rapid heartbeat.
Annabelle A. Veerapaneni, a medical oncologist and hematologist at Northwestern Medicine, emphasized the importance of early detection. She advised patients to seek medical attention for any unusual symptoms. The CDC recommends immediate evaluation if swelling appears in one limb but not the other, or if breathing difficulties arise without explanation.
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Other factors influence risk. Obesity, central venous catheters, and prolonged inactivity can all raise the chances of clotting.
If a clot forms, treatment usually involves blood thinners to prevent it from growing. Treatment duration varies; some patients remain on blood thinners for the entire course of cancer treatment or longer.
Patients should discuss their personal risk factors with their care team. They can ask whether their cancer type increases clot risk, and which physical activities are safe during treatment. Understanding the side effects of preventive drugs helps patients make informed decisions.
Avan Armaghani, a medical oncologist specializing in breast cancer at Moffitt Cancer Center, stressed the importance of awareness. “If something doesn’t feel right, tell your health care team,” she said. “That’s what we’re here for.”
Many patients remain unaware of financial aid options that could ease the burden of treatment costs. Caregiver expenses also differ widely depending on location, adding another layer of complexity to cancer care.
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