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Colorectal Cancer

Woman holding model of colon

What is colorectal cancer?

Colorectal cancer is the term used to describe any type of cancer that affects the colon or rectum.

The colon (also called the large bowel) is the part of the digestive system that turns what remains of our digested food into solid waste before expelling it from the body. Colorectal cancer may also be called bowel cancer, colon cancer, or rectal cancer.

What causes colorectal cancer?

Cancer is the uncontrollable growth of cells. It occurs when a mutation or abnormal change upsets how cells multiply and divide. This allows cells to keep dividing out-of-control, instead of dying and being replaced by new cells. Sometimes these out-of-control cells cluster together and form a lump called a tumor. Tumors can form in almost any area of the body,

Experts are not sure why colorectal cancer develops in some people but not others, but they have identified a number of risk factors that make people more likely to develop colorectal cancer. These include:

  • Age: 91% of cases are diagnosed in people older than 50
  • Polyps in the bowel (these can be identified up during a colonoscopy). Most colon cancers develop within a polyp
  • People who eat diets low in fiber and high in animal protein (red meat), saturated fats, and calories
  • High alcohol consumption
  • A family history of colorectal cancer or people who have inherited certain genes
  • Excessive weight
  • Smoking
  • Low levels of physical activity
  • A history of inflammatory bowel disease (eg, Ulcerative Colitis or Crohn’s) or irritable bowel disease
  • A previous history of breast, ovary, or uterine cancer.

What are the symptoms of colorectal cancer?

Symptoms may vary depending on where the cancer is located and its size but may include:

  • A change in bowel habits (for example periods of diarrhea followed by periods of constipation)
  • A lump in the abdomen or rectum felt by a doctor
  • A feeling like the bowel is not completely empty after a bowel movement
  • Abdominal pain
  • Bloating or feeling full even after not eating for a while
  • Blood in the feces (these may give the stools a tarry or black appearance) or coming from the rectum
  • Fatigue
  • Unexplained weight loss
  • Unexplained iron deficiency.

See your doctor if any of these symptoms persist for more than four weeks and there is no apparent reason for them.

How is colorectal cancer diagnosed?

If colorectal cancer is suspected based on your symptoms or the results of screening or another test, further tests will be conducted before a definite diagnosis is made. These may include:

  • A digital rectal examination
  • An x-ray of the digestive tract
  • Blood tests
  • Colonoscopy (usually needed for a definite diagnosis unless cancer has been found during an unrelated surgery).

How is colorectal cancer treated?

Treatment for colorectal cancer depends on the type of cancer, if it has spread, and where it is located.

Treatment may include:

  • Surgery
  • Chemotherapy
  • Radiation therapy.