Colorectal cancer, colon cancer, rectal cancer

A cancer is a growth of an abnormal group of cells that do not follow the rules of their organ and the body.  Cancer cells do not function normally and may grow at an out-of-control rate so that these abnormally-functioning cells crowd out the normally-functioning ones.  Eventually, the organ no longer works.  In addition, just the sheer mass of the cancer cells can cause trouble by blocking one of the body’s tubes, such as the colon.  Cancer cells can grow into adjacent organs, damaging them, and also spread (metastasize) to other organs by way of the blood stream, thus colonizing the body and multiplying their deleterious effects.

Cancer of the colon and rectum are the same cancers, just different locations.  The rectum is the lowest 15 centimeters of the bowel and a cancer occurring there is called rectal cancer.  Cancers in the colon, above the rectum, are called colon cancers.  While rectal cancers are more likely to present with bleeding than colon cancers, the only real differences between them is in treatment, since rectal cancers are within the pelvis and this creates anatomic challenges.  To make things simple, we usually call them colorectal cancers which just encompasses all of the cancer locations in the colon and rectum.

Colorectal cancer is the number one cancer killer in Canada amongst non-smokers.  There are a variety of ‘risk factors’ for developing it, including family history, colorectal polyps, ulcerative colitis, etc., but the most important risk factor is increasing age.  Fully 75% of patients with colorectal cancer do not have a family history, so that most cases occur in unsuspecting patients without any particular explanation.  Hence the need for screening beginning at a certain age.

We think that about 95% of colorectal cancers develop from polyps.  Certain polyps gradually develop characteristics of a cancer.  The ‘poly-cancer sequence’ is thought to take from 7 to 15 years, although sometimes a very small early polyp will inexplicably have malignant changes in it.  Generally the larger the polyp, the more likely it is undergoing such transformation.  Polyps greater than one centimeter in diameter are considered as becoming significantly large in this consideration.  However, as noted, small polyps can sometimes cause trouble.  See Polyps.

In addition, there are no particularly diagnostic symptoms of colon cancer.  Patients may present with a wide variety of symptoms.  Diagnosis usually requires scoping of the colorectum by a specialist.  This does crate a problem since access to specialists and scoping can be difficult in come centers.

Treatment is surgical.  If the cancer is in the colon or in the upper half of the rectum, the portion of the bowel containing the cancer can be removed and the remaining ends of the bowel usually rejoined so there would be no need for a stoma ‘bag’.  If the cancer is low in the rectum, the surgeon may have to remove the entire rectum and sphincter muscles to get it out and this could leave the patients with a colostomy.  There may be associated radiation treatment if the cancer is in the rectum, and there may be additional treatment by chemotherapy if the cancer is locally advanced into adjacent lymph nodes, in either rectal or colon or cancer.

The cure rate for colon cancer is about 50 – 60%.  Patients must wait 5 years to know if they are cured.  Those that are well at three years have a high likelihood of being cured.

© Pezim Clinic, Vancouver, British Columbia, Canada