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MEDICINE 101

MINI-MEDICAL- CANCER

This year 125,000 Canadians will be newly diagnosed with cancer.   Sixtyfive thousand of us will die from it.   Two thirds of all new cancers will be diagnosed in those aged 65 or older and, though we can now cure about 50% of all cancers, it is still one of the commonest causes of death in our society, second only to heart disease.

Just saying the word cancer invokes a feeling of dread, but the word is an old one.   It's derived from the Greek word KARKINOS meaning crab.   Ancient physicians, dissecting out cancers thought the swollen veins that surround the cancer resembled the legs of a crab.

But what goes wrong in cancer, how does the crab-like growth begin and why?  Here's Dr. Paul Caldwell on how cancer works.

START HERE

There are many forms of cancer and they all have their own unique properties.  But every cancer shares two abnormalities -

1.  cancer cells multiply and grow in an uncontrollable fashion and 2.  they invade the tissues around them.

Though we're not usually aware of it, many cells in your body are constantly growing, replacing old cells that are dying.  But there is a sophisticated system in place to be sure that you don't over-produce cells.  It's even more complicated; your body has a system to produce more cells than usual if needed.   For example if you cut your skin new cells grow quickly to fill in the gap and heal it.   The amazing thing is, once the cut has healed, the extra skin cells somehow know to stop growing – you grow what you need and no more.

Well, cancer cells don't do that.    Within the nucleus of cancer cells the DNA somehow becomes different than that of normal cells.   This DNA directs the cancer cell to begin to divide, to multiply and produce other cancer cells – and, to simply keep on doing that again and again and again, free from the normal controls.  Here's a picture showing normal cells dividing, and here's another picture showing cancer cells dividing.   This uncontrollable and abnormal cell division is the hallmark of cancer.

Cancer begins with only one or two microscopic cells that divide like this, but these cells divide quickly --  The cancer will be the size of a small grape by three and a half years and a year later – it would weigh about a kilogram.

The second characteristic of cancers is that they don't stay home, they invade the tissue next to them.  This is the property that makes a tumor malignant (the word comes from the French MAL, meaning bad).   Many cancer cells spread not only to the tissues around them but to distant parts of the body – cells break off from the original cancer and travel by way of lymph channels or blood vessels to other organs.   This is called metastasis.

Treatment of the cancer focuses on the cancer cell's tendency to multiply.  Radiation and chemotherapy for example (kill all cells, health and normal, as they divide.  But these treatments damage cancer cells much more than they damage normal cells, because the cancer cells are dividing so much more rapidly than others.

(If scientists could just figure out how to stop these two properties – unregulated cell division and the tendency to spread – cancer could be beaten.)

We believe that most cancers are caused by a combination of genetic or inherited tendencies and exposure to some kind of irritant over a lifetime, but these two properties – the unregulated cell division and the tendency to invade or spread to other areas are the biological hallmarks of this disease.