Blood Clots, DVT, Pulmonary Embolism, and Cancer

• Sudden shortness of breath, or breathlessness that gets worse over minutes to hours.
• Chest pain that is sharp and worse when you breathe in.
• Coughing up blood.
• Fainting, near-fainting, or a resting pulse above 100 that will not settle.
• A leg or arm that becomes swollen, red, and painful over hours, especially on one side only.

Do not drive yourself. Do not massage the limb. Do not take an extra dose of a blood thinner on your own.

This page is part of a set awaiting clinician review before it goes live to the public. Follow your current oncology and emergency instructions now.

This is not bad luck. It is not just lying around too much either. Tumor cells release tissue factor, a protein that sets off clotting. Some cancers also make a substance that acts straight on Factor Xa in the clotting chain. The blood really is more likely to clot.

The size of the effect is measurable. A Dutch study of 3,220 people aged 18 to 70 found the risk of a vein clot was 7 times higher in people with cancer. A study in Minnesota found a 4-fold rise. It was higher still during chemotherapy. Reported rates in cancer run as high as 20%.

Risk is not evenly spread. The Dutch study found the highest risk in the first few months after diagnosis, and the highest increases in blood cancers, lung cancer, gastrointestinal cancer, and cancer with distant spread.

Arteries are affected too. That is less widely known. One study matched 279,719 pairs. The 6-month rate of heart attack was 2.0% in people with cancer and 0.7% in controls. Stroke was 3.0% versus 1.6%. People with cancer who had an artery clot had a 3-fold higher hazard of death.

Several chemotherapy drugs independently raise clot risk: methotrexate, cyclophosphamide, cisplatin, doxorubicin, fluorouracil, and lenalidomide.

Lenalidomide is the clearest case. Its label carries a boxed warning for venous and arterial thromboembolism, listing deep vein thrombosis, pulmonary embolism, heart attack, and stroke in myeloma patients taking it with dexamethasone, and it recommends preventive anti-clotting treatment. Multiple myeloma covers where that combination is used.

NHLBI notes that deep vein thrombosis usually forms in the lower leg, thigh, or pelvis, but can also occur in the arms, especially when a large intravenous central line sits in the vein.

If you have a port or a PICC line, an arm that becomes swollen, heavy, or achy on that side is not a strain. Neck or shoulder swelling on the same side counts too. Central line and PICC troubleshooting covers what else to watch for.

NHLBI puts the national scale at as many as 600,000 venous thromboembolism events each year in the United States, across all causes.

For people admitted to hospital with cancer, NCCN guidelines recommend preventive anticoagulation with unfractionated heparin or low molecular weight heparin.

There are clear exceptions. In those cases drugs give way to leg compression devices. The exceptions are active bleeding, a platelet count below 50,000 per microliter, a bleeding-related clotting disorder, or an epidural or similar spinal catheter in place. Compression has its own limits. It is not used if a deep vein clot is already there, or if leg artery disease is severe.

After abdominal or pelvic cancer surgery, prevention continues for up to four weeks after the operation, not just until discharge. If you were sent home with injections and a stop date, that is why.

The Khorana score is a risk calculator for people with solid tumors on chemotherapy. In those who score high, a direct oral anticoagulant or low molecular weight heparin cut the rate of lung clots. For myeloma patients on immunomodulatory drugs, the IMPEDE VTE score guides the choice between aspirin and full anticoagulation.

One finding argues against extending prevention for everyone. A meta-analysis cited by StatPearls looked at standard versus extended courses in people with cancer hospitalized with an acute illness. Clot risk was not lower with the longer course. Bleeding risk was about twice as high.

Low molecular weight heparin, an injection under the skin, has long been a mainstay for clots linked to cancer. The dose is worked out from your weight, and it is lowered or avoided if your kidneys are not clearing it well. Ask which blood thinner is being chosen for you, and why that one.

Tablets are now a real alternative. In the Caravaggio trial, apixaban was non-inferior to low molecular weight heparin for treating cancer-associated clots, without an increase in major bleeding. Rivaroxaban, edoxaban, fondaparinux, and warfarin are also used.

Duration is longer than most people expect. NCCN advises at least 3 months, or as long as the cancer is active. For a leg or lung clot not caused by a catheter, the advice is anticoagulation with no set end date. It should be reviewed often rather than stopped on a schedule.

If the clot is around a catheter, treatment is either removing the catheter or anticoagulating while it stays in.

When anticoagulation is impossible, for example during active bleeding, a retrievable filter may be placed in the vena cava for clots in the vena cava, iliac, femoral, or popliteal veins. These are meant to come out. Ask when yours will be reassessed for removal.

Clot-dissolving drugs are reserved for a clot threatening life or limb, and are avoided with brain tumors or brain metastases, active bleeding, or previous bleeding into the brain.

• Does my specific cancer and current drug regimen put me in a higher clot risk group?
• Am I being scored with the Khorana or IMPEDE VTE tool, and what did I score?
• If I am on a blood thinner, which bleeding signs bring me straight back?
• How long is my anticoagulation planned for, and what would end it?
• Do I need to stop anything before my next procedure, and who tells the surgeon?

Creating a cancer symptom and call plan helps turn those answers into a written page you can keep on the fridge.

Anticoagulants work by making clotting harder, so the warning signs run in both directions. Seek urgent care for:

• Blood in vomit, or vomit that looks like coffee grounds.
• Black tarry stools, or visible blood in stool or urine.
• A headache that starts suddenly and is severe, or any head injury while on a blood thinner.
• Bleeding from a cut that will not stop after 10 minutes of firm pressure.
• Large bruises appearing without any injury.

• StatPearls (NCBI Bookshelf) — Cancer-Associated Thrombosis
• National Heart, Lung, and Blood Institute — Venous Thromboembolism
• DailyMed (National Library of Medicine) — REVLIMID (lenalidomide) prescribing information