Cancer patients have an elevated risk of developing life-threatening blood clots. For some patients, the type of cancer they have can trigger blood clots. Some cancers actually produce substances which can activate the clotting cascade and produce blood clots (thrombosis).
A thrombosis can also be triggered by tumors that compress blood vessels and slow the flow, increasing the risk for a clot to form. Additionally, some cancer drug therapies (i.e. Tamoxifen, progestins, aromatase inhibitors, thalidomide, cisplatin, antiangiogenic agents, etc.) and radiation therapy can cause inflammation and injure vascular endothelial walls, a set up for thrombosis.
These 3 conditions (hypercoagulability, stasis, vessel wall injury) make up what is famously known as “Virchow’s triad,” which predispose a person to the development of venous thrombosis.
A deep vein thrombosis (“DVT” is a blood clot most often in the deep veins of the leg, pelvis or arm) or pulmonary embolism (“PE” is a blood clot in the lung) occurs more commonly among those with certain risk factors:
- Having cancer (especially pancreatic, brain, gastric and any metastatic cancers); if you develop a blood clot there is a 420% higher risk of being diagnosed with any cancer in the next 6-months (REF)
- Recent major surgery or trauma
- Having a central venous catheter (such as a chemotherapy mediport and dialysis shunts)
- Receiving drugs that increase the risk of blood clots (such as Tamoxifen, birth control pills, hormone replacement therapy)
- Being overweight or obese
- Physical inactivity
- History of a prior stroke (or transient ischemic attack)
- Prolonged hospitalization or bed rest; even short periods (i.e. a few hours) of inactivity can increase your risk
- History of a heart attack or coronary artery disease
- Having peripheral artery disease (a narrowing of arteries due to atherosclerosis, most commonly in the pelvis and legs)
- History of a prior blood clot (or family history of blood clots); check with your doctor whether you have an underlying condition that makes your blood clot more easily. If you have a history of blood clots or a heart condition that predisposes you to blood clots, your doctor will weigh the pros and cons of prescribing a blood-thinning medication for you.
- High blood pressure
- Having vasculitis (a disorder that causes blood vessels to become inflamed)
- Having varicose veins
- Having heart failure (a condition in which the heart is damaged and can’t adequately pump blood)
- Having atrial fibrillation (and abnormal heart rhythm)
- Having diabetes
- Having metabolic syndrome (defined as having 3 or more of the following:
- 1) Abdominal obesity (Waist circumference of greater than 40 inches in men, and greater than 35 inches in women)
- 2) Triglyceride level of 150 mg/dL or greater; optimal is 80 mg/dL or lower
- 3) HDL cholesterol of less than 40 mg/dL in men or less than 50 mg/dL in women; optimal is 60 mg/dL or higher
- 4) Systolic blood pressure (top number) of 130 or greater, or diastolic blood pressure (bottom number) of 85 or greater; optimal blood pressure is 115/75 or lower
- 5) Fasting glucose of 100 mg/dL or greater; optimal is 85 mg/dL or lower
- High LDL; <70 mg/dL is optimal
- High total cholesterol levels; less than 200 mg/dL is optimal
- Having a low red blood cell count (anemia), having a high platelet count or having a high white blood cell count
- Elevated levels of the amino acid homocysteine (which can be caused by many factors): less than 8 micromol/L is optimal
- Elevated levels of the inflammatory proteins high-sensitivity C-reactive protein (less than 1 mg/mL is optimal) and fibrinogen (less than 370 mg/dL is optimal)
- High blood sugar levels
- Drinking more than 1 serving of alcohol per day
- A variety of other conditions (i.e. thyroid abnormalities, pregnancy, high blood fibrinogen levels)
- Dehydration can cause your blood to thicken
- Having hyperthyroidism (an overactive thyroid)
How to Reduce Your Risk of Blood Clots
- Treating conditions that can increase the risk of blood clotting (see the list, above)
- Talk with your doctor about ways to lower your homocysteine level if it is high
- Your doctor may prescribe medications before, during or after surgery to reduce the risk of excessive blood clotting
- Avoiding medications that increase the risk of blood clotting
- Move your legs frequently while you’re sitting
- Exercise regularly (goal: at least 30 minutes of moderate aerobic exercise, five days per week)
- Maintain a healthy weight
- Stop smoking (and avoid second-hand exposure)
- Reduce your stress levels
- Wear loose-fitting clothes, stockings or socks
- Wear compression stockings if your doctor prescribes them (these can reduce the risk of DVT among airline passengers on flights lasting more than 4 hours) REF.
- Stay well-hydrated (if your urine is a pale yellow color or clear, you are probably drinking enough)
- Consider taking a low dose of aspirin daily; this is thought to cut your risk of developing blood clots by 40%. The active ingredient in aspirin is a plant-derived compound called a “salicylate;” instead of taking a baby aspirin, you could consume foods that have high salicylate content, which includes many fruits, vegetables, spices, herbs and beverages. (Learn about the benefits and risks of taking aspirin)
- Eat foods rich in vitamin E, which helps to thin blood (e.g., nuts, cold-pressed nut and seed oils, avocado, oats, wheat germ)
- Eat foods rich in omega-3 fatty acids, which also help to thin blood (e.g., oily fish, flaxseed, sunflower seeds, green leafy vegetables). One study of nearly 22,000 individuals reported that those who consumed >4.7 grams per week of marine omega-3 fatty acids (from either fish or supplements) had a 22-26% lower risk of developing a DVT and 39-60% lower risk of developing a PE.
- Avoid inflammatory trans fats
- Avoid excessive intake of saturated fats, sugar and salt
- Consider foods and supplements that reduce blood clotting: curcumin, polyphenol-rich foods (brightly colored fruits, vegetables and berries, olive oil) and drinks (green and black tea), foods rich in vitamin C (citrus, peppers, cruciferous vegetables, watercress, strawberries, spinach), garlic, onions, tomatoes, Gingko biloba, rutin (plant flavonoid), Danshen Compound Tablet (a traditional Chinese medicine formula: Salvia miltiorrhiza, Panax notoginseng and Borneum syntheticum), nattokinase (fermented soybean product)
Did you know that in otherwise healthy airline passengers who are flying for greater than 4 hours, the risk of developing a DVT is 3-12%? (REF); this risk is higher for those with a cancer history.
One study found that even with exercises done while flying, the risk of developing a blood clot was 8% during a 7-8 hour flight. Impressively, this risk was completely abolished (as assessed by ultrasound) by preventively taking one capsule (Flite Tabs) containing nattokinase and pycnogenol (a tree bark extract) 2 hours before and 6 hours into the flight (REF).
Should You Avoid Vitamin K?
No. Not only are the K-vitamins (there are in fact three: K1, K2 and K3) essential for healthy blood clotting and strong bones, they may also have anticancer effects.
In a Canadian study, for instance, 440 postmenopausal women with osteopenia (weakened bones) took a vitamin K1 supplement for two years. Bone loss wasn’t halted but taking vitamin K1 was associated with an amazing 75% reduction in cancer incidence. Another study published in the American Journal of Clinical Nutrition comprising 24,340 participants found that a higher intake of vitamin K2 was associated with a reduced risk of cancer. Furthermore, many foods that are rich in vitamin K – such as green and cruciferous vegetables — are also high in antioxidants and anti-cancer compounds.
Vitamin K1 poses a dilemma for some people with cancer, however: On the one hand, they are advised to eat lots of green vegetables because these are rich in anticancer compounds; on the other hand, these very foods are high in vitamin K1, which promotes clotting. And for anyone who is taking warfarin, a blood thinner, this can cause problems.
Warfarin is a blood-thinning medication that’s prescribed to treat and prevent blood clots. Certain foods and beverages can make warfarin less effective in preventing blood clots, and one these is vitamin K. This doesn’t mean you have to avoid vitamin-K-containing foods completely; however, it’s important to be consistent in how much vitamin K you get from your food and supplements daily. If you are taking warfarin, limit your daily intake of vitamin K1 to 90 mcg/day (women to 120mcg/day (men).
To illustrate what that means:
- ½ cup cooked kale contains 531 mcg vitamin K
- ½ cup cooked spinach contains 444 mcg
- ½ cooked Swiss chard contains 287 mcg
- 1 cup cooked broccoli contains 111 mcg
More vitamin K content data available here.
How is a DVT Diagnosed
In most cases, a diagnosis is made with a history, physical examination, venous ultrasound and a blood test (D-dimer, a fibrin degradation product that is more than 95% sensitive for a venous thromboembolism)
How is a PE Diagnosed
As with a DVT, a history, physical examination, venous ultrasound and a D-dimer blood test are first assessed. If there is a high degree of suspicion for a PE, a CT angiogram and echocardiogram (ultrasound) of the heart may be recommended.
Depending on the size and location of the blood clot, you may need emergency or routine treatment.
This is indicated when blood clots can damage tissues and organs (such as stroke, heart attack, kidney failure, DVT or PE). Treatment may include clot busting drugs, called “thrombolytics;” (Example: tissue plasminogen activator or tPA), venous filters (i.e. inferior vena cava filter) or interventional procedures to remove the blood clot (thrombectomy).
In a non-emergency situation, blood thinning medications, also called “anticoagulants,” are used to keep existing blood clots from getting larger and to prevent new blood clots from forming; (Examples: warfarin, heparin, enoxaparin, dabigatran, rivaroxaban, apixaban ) Antiplatelet drugs may also be recommended (Example: aspirin, clopidogrel, prasugrel, ticagrelor)