Dr Stanley Yu, Specialist in Clinical Oncology, looks at some misconceptions about deep vein thrombosis (DVT) – particularly, how the illness affects people who are undergoing cancer treatments. Statistically, around 50 percent of cancer patients are at risk of some form of thromboembolism, including DVT in the legs or elsewhere. It’s therefore important to be aware of this preventable disease, why you might have no DVT symptoms, and treatment options.
Myth #1: Varicose veins are the same as thromboembolism
In fact, they are completely different diseases. Venous thromboembolism (VTE) refers to clot formation in the blood vessels. It includes deep vein thrombosis (DVT), which is when a blood clot develops in a deep vein. The most common site for this is the lower limbs. When the clot breaks loose and travels through the bloodstream to the lungs, it can lead to pulmonary embolism (PE).
On the contrary, varicose veins are twisted, dilated superficial veins in the limbs or body. Varicose veins develop when the valves inside the veins stop working properly; blood then flows backwards and collects in the veins. However, this does not directly lead to blood clot formation.
Myth #2: If you’re not bedridden, you don’t need to worry about DVT
It is true that long-term bed rest is one of the major risk factors for DVT. Immobility reduces the blood flow in lower limbs and blood may stagnate as a result, and become “sticky”. Furthermore, a bedridden patient may not drink as much water as usual, resulting in dehydration. This is especially true for those with advanced-stage cancer and can result in a higher risk of clot formation.
Being bedridden is unlikely to be the sole factor. In fact, cancer cells themselves can activate the clotting cascade and turn blood “thick” and “sticky”. This explains why cancer patients are more prone to having DVT. Furthermore, some medications can also escalate the risk of a clot forming. For example breast cancer patients on certain types of hormone therapy are found to be at three times more risk of thromboembolism. Patients on chemotherapy are at six times more risk of DVT than those who are not.
Myth #3: DVT only occurs in the legs
DVT mostly happens in the lower legs, thighs or pelvis, but it can also occur in other body parts including the arms, brain, intestines, liver or kidneys. Patients may have localised pain. DVT in the legs can become life-threatening when the blood clot breaks off, then travels through the heart and gets stuck in the blood vessels of the lungs. Such a situation is called pulmonary embolism (PE). It can cause several serious complications including cardiac arrest, cardiac arrhythmia, pleural effusion, pulmonary hypertension and pulmonary infarction.
Myth #4: There are observable symptoms of PE
Pulmonary embolism can be silent in the early stages. Only when it progresses over a period of time might patients start to suffer from difficulty in breathing, a cough, coughing up blood, sharp and sudden chest pain – and, most seriously, sudden death. Unfortunately, due to the invisibility of DVT symptoms, most cases are at an advanced stage when being diagnosed.
To assess the presence of DVT, a physician may arrange blood tests, a chest X-ray, a Doppler ultrasound, an echocardiogram and/or a pulmonary angiogram.
Myth #5: Anticoagulants are unsuitable for patients having cancer treatment
Even for cancer patients who are currently on cancer treatments, anticoagulants are mostly not contraindicated to tackle DVT and prevent a potentially fatal pulmonary embolism from happening. Anticoagulants can prevent blood clot formation and they can “dissolve” blood clots. This avoids the issue of clots breaking off from blood vessels from deep veins in the lower limbs and moving upward along the venous blood vessels and causing PE. As medical treatment advances, there are newer types of anticoagulants available. These will have lower risks of food-drug and drug-drug interactions, including those with cancer treatment.
Furthermore, if the patient is on any type of anticoagulants, they’re advised to inform and consult their physician prior to surgery. This is to reduce the risk of massive bleeding.
Myth #6: DVT can’t be prevented
DVT is a preventable disease. However, cancer patients can be six to seven times more prone to develop DVT symptoms or suffer from DVT than other people. There are certain measures that can be taken to minimise the risk. Most cancer patients will require surgery, and many become bedridden for a period as a result. They should consult their doctor to see about a low dose of anticoagulant as a precautionary DVT treatment. Moreover, they can wear TED (thrombo-embolus deterrent) stockings and keep hydrated. Plus, start mobilisation after surgery earlier and exercise regularly after an operation.
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