Bowel cancer occurs when abnormal cells in the wall of the large intestine grow in an uncontrolled way. Bowel cancer refers to any cancer that starts in the large intestine.  It is also referred to as colon cancer, rectal cancer or colorectal cancer, depending on where it is found in the intestine.

the digestive system

How does bowel cancer develop?

Bowel cancer develops from polyps.  Polyps are small growths on the inner lining of the large bowel that are caused by an abnormally fast reproduction of cells.  Most bowel polyps are not cancerous.  Some polyps may become cancerous if left to grow into tumours.  It is important to remove polyps when found.

How does bowel cancer spread?

Bowel cancer can spread when cancer cells break off from the cancerous tumour and travel through the bloodstream or lymphatic system to other parts of the body.  This is called metastasis.  It’s not uncommon for bowel cancer cells to spread to other parts of the bowel or to other body parts such as the liver, the pelvis or the abdomen.

What causes bowel cancer?

Bowel cancer is caused by the mutation of genes that cause cells in the large intestine to reproduce abnormally and form polyps.  While the polyps may start as benign, some can become cancerous.  If a polyp does become cancerous, it can lead to the spread of cancer through some or all of the tissue layers making up the colon and rectum. This often occurs over several years.

Polyp removal

Polyp removal

What different types of bowel cancer exist?

There are several different types of bowel cancers.  Each one is identified by the type of cells in which it originated.  About ninety-five percent of bowel cancers are adenocarcinomas and start in the gland cells in the lining of the bowel wall.

Other types of bowel cancer include the following:

  • Squamous cell cancer, which is a rare cancer which starts in the skin-like squamous cells that make up the lining of the bowels.
  • Carcinoid tumours, which are rare, slowing-growing tumours produced by hormone producing tissues. Though it is usually in the digestive system, it is treated differently than bowel cancer.
  • Gastrointestinal stromal tumours, which start from the interstitial cells of Cajal in the wall of the colon. Not all of these tumours are malignant.
  • Lymphomas, which typically start in the lymph nodes, may also start in the bowels or other organs.
  • Sarcomas, which are tumours that may grow in the blood vessels, muscles and connective tissues.

Treating and preventing bowel cancer

Treatments for bowel cancer include surgery, radiation and chemotherapy, depending on the stage of the cancer and how far it has spread.

Bowel cancer is usually treatable if caught early.  Regular screenings are an important step in prevention.

Bowel cancer screening kit

Bowel cancer screening kit

Some factors associated with the development of bowel cancer such as family history and age cannot be prevented.  If there is a family history of bowel cancer or you are over the age of 50, it is important to be screened on a regular basis.

An emerging body of research is indicating that knowing a tumour’s genomic profile could be more important for successful treatment than knowing its location or size. As each tumour’s genomic profile is unique, this approach is often referred to as personalised or precision medicine.

Research suggests that a healthy diet rich in fiber from fruits, vegetables and whole grains along with regular exercise can reduce the risk of bowel cancer.