Ask the Pharmacist

Q) My oncologist spent several minutes with me today going over the symptoms of a blood clot. Why would she bother doing that?

A) It is a fact, often overlooked amidst all the other concerns that a cancer diagnosis brings, that cancer itself greatly increases the risk of an individual being afflicted by a blood clot. Data suggests that up to 20% of patients with cancer will experience a clot which is roughly 4-5 higher than the general population.

In fact, thrombosis (the medical term for blood clots) is the second leading cause of death among cancer patients next to, of course, the cancer itself. Interestingly, the reciprocal runs true as well. That is, patients who have had a blood clot are more likely to be diagnosed with cancer at some point in time.

Some experts say that about 1 in 10 people who are diagnosed with DVT (Deep Vein Thrombosis are clots that form in deep veins, usually in the leg) will be diagnosed with cancer within a year, although other experts believe that number is greatly exaggerated.

Getting back to why cancer sometimes causes clots, there are several reasons why this occurs.

The first comes down to simple (?) genetics. Some of the genetic changes that we undergo that cause cancer also increase the activation of what are known as clotting factors. Clotting factors are proteins in our blood that serve a vital function when we are bleeding by causing a chain reaction that eventually leads to a substance in our blood turning into long strands of fibrin that combine with platelets that grow into a clot. Normally, our body does an excellent job of balancing when blood should clot and when it should not, but cancer can mess this up. When these clotting factors are turned on, there is an increased potential for clots where we don’t want them, namely internally in our extremities, or even worse, our heart, brain or lungs.

Another factor that can increase the risk of cancer patients suffering from clots is that many of the chemotherapy drugs that are used to fight cancer have the unfortunate side effect of once again increasing the activation of these clotting factors. Additionally cancer cells themselves damage tissue in our bodies as they reproduce rapidly into tumors which push into the surrounding tissues as they grow. This leads to swelling and inflammation which in turn triggers clotting.

Lastly, these tumors also produce a myriad of chemicals some of which, perhaps not surprisingly at this point in our discussion, once again can activate our clotting factors. Not everyone with cancer is at the same level of risk from thrombosis. Having a specific condition can further increase your risk of having a blood clot such as:

· a prothrombin gene mutation
· a protein C or S deficiency
· an antithrombin III deficiency
· or one of a number of inherited disorders such as the Factor V Leiden mutation

The type of cancer can also increase the likelihood of having a clot. Cancer of the:

– Liver
– Kidney
– Lung
– Ovaries
– Pancreas
– Stomach
– Uterus
– Blood (leukemia & lymphoma)

are all more likely to cause a clot than other types of cancer as well as cancer that has spread to other areas of your body (what we call a metastatic cancer).

There are several other reasons that having cancer can raise your chances of having a clot. First is that many people (although certainly not all) with cancer spend more time being static (i.e. not moving around as much as is normal) which causes blood to pool and be more inclined to clot.

As well, sometimes treatment can require surgery which is frequently, independently of cancer, associated with clots (especially surgery to the hips or abdomen). You may have had a central venous catheter inserted into you which is a tube that is used to give certain medications which again increases your clot risk.

A few patients at high risk will be put on one of several drugs to prevent a clot from occurring but the vast majority will be dealt with (or at least should be) in the same way that the patient above was. Namely, they will be educated on the symptoms of a clot and informed that if they recognize these occurring within them, they seek medical attention immediately. Perhaps the one nice thing about clots such as DVT is that their symptoms (when you feel them, some do not feel any symptoms until they are life-threatening) are fairly recognizable and specific so they are harder to miss or misdiagnose unlike so many of the viruses we have been dealing with over the last couple of years.

These symptoms can include:

  • A sudden pain (or cramping, soreness or tenderness) and swelling in one of your legs (theoretically it could happen in both, but that would be extremely rare and indicative of terribly bad luck) more likely in the soft tissues such as a calf or thigh or even the pelvis.
  •  Red or discoloured skin where the pain is emanating from
  •  Sharp chest pain
  •  A fast pulse or irregular heart rate
  •  Bloody cough
  •  Sudden onset of shortness of breath
  •  Sweating or a fever
  •  Severe abdominal pain, vomiting or diarrhea

The other good news about this situation is that, once recognized, we have a number of pharmaceutical options that are extremely effective at dissolving the clot often without a trace of it ever having occurred (although some will continue to have pain and swelling in the area for a prolonged period of time.).

Better than treating them is preventing them of course. So for those of us with a cancer diagnosis, make sure you stay adequately hydrated, stretch your legs, move around as much as you can and for heavens sake, quit smoking (which is a significant risk factor for clots, as well as cancer somewhere else in the body!!). For more information about this or any other health related questions, contact your pharmacist.