This 3-D image of a colonoscopy was compiled using X-rays taken with a CT scanner. (Dr. Perry J. Pickhardt/ University of Wisconsin Medical School/Associated Press)

It's not one of those high-profile diseases that attracts A-list celebrities to raise awareness and money. Yet colorectal cancer is the third most common cancer in Canada behind breast and lung cancer in women and prostate and lung cancer in men.

Approximately 21,500 new cases will be diagnosed in Canada this year, according to the Canadian Cancer Society. Around 8,900 Canadians will die from the disease every year. One in 14 men are expected to develop colorectal cancer during their lifetimes, and one in 27 will die of it. Among women, one in 16 are expected to develop colorectal cancer during their lifetimes, and one in 31 will die of it.

According to the Canadian Cancer Society, Newfoundland and Labrador have the highest incidence rates among men in the country. Among women, rates are highest in Prince Edward Island. Around the world, more than 639,000 people succumb to the disease every year, according to the World Health Organization.

Former Toronto Maple Leafs head coach Pat Burns beat it, as did former journalist and Canadian consul-general in New York, Pamela Wallin.

Former U.S. president Ronald Reagan had a bout with the disease in 1984-85. Surgeons removed a 50-centimetre section of his large intestine to get rid of a tumour that threatened his life.

Charles Schultz, the creator of the Peanuts cartoon strip, battled it, as did former baseball star Darryl Strawberry.

Sharon Osbourne, wife of rock star Ozzy Osbourne, beat the disease and has devoted much of her time to raising awareness of colon cancer.

American television personality Katie Couric lost her 42-year-old husband to it. She became an advocate for screening for the disease while hosting a morning talk show and was credited with prompting a big jump in the number of people who underwent testing.

What is colon cancer?

It's a malignant tumour that develops over a period of time — at least 10 years — usually on the wall of the large intestine. As it grows, it can move on to other organs.

Approximately two-thirds of these cancers are found in the large intestine and one-third in the rectum. Colorectal cancer usually develops from benign tumours or polyps found in the bowel.

What are the symptoms?

Because tumours associated with colorectal cancer are so slow to grow, symptoms may not appear until the cancer has progressed to the later stages of the disease.

Symptoms may include:

• Fatigue and weakness.
• A change in bowel habit (alternating constipation and increased stool frequency).
• Stool streaked or mixed with blood.
• Diarrhea, constipation, or feeling that the bowel does not empty completely.
• Stools that are narrower than usual.
• General abdominal discomfort (frequent gas pains, bloating, fullness, and/or cramps).
• Weight loss with no known reason.
• Nausea and vomiting.

What are the risk factors for developing colon cancer?

Age is one of the key factors. The older you are, the more likely you are to develop colon cancer. The vast majority of cases are diagnosed in people between the ages of 50 and 74.

Heredity is another factor. If someone you are closely related to had the disease, your chances of developing it are much higher.

Other factors include:

• A diet high in red meat and low in fruits and vegetables may increase your risk.
• Obesity and a lack of physical activity increase the risk.
• Alcohol, especially beer, may increase your risk.
• Smoking also increases your risk.

How can I avoid getting it?

There are a few tests health professionals can administer, including:

• A digital rectal exam (DRE), in which a doctor inserts a lubricated, gloved finger into the rectum to feel for abnormal areas. It only detects tumours large enough to be felt in the distal part of the rectum and is not really a screening test.
• Fecal occult blood test (FOBT), which checks for blood in the stool and can help identify polyps before they become cancerous.

But the most effective way to check for the early signs of colorectal cancer is through a colonoscopy. A doctor inserts a lighted probe into the rectum and through the entire large intestine to look for polyps and other abnormalities that may be linked to cancer. The advantage to the colonoscopy is that if polyps are found, they can be removed right away. Tissue can also be removed and sent off for tests.

Many people find the colonoscopy an unpleasant experience, but this can be lessened if a sedative is administered. For most, preparing for the colonoscopy is more difficult than the actual procedure. The night before, you are required to consume a large quantity of laxative to thoroughly clean out your bowels.

Virtual colonoscopies have been gaining in popularity in recent years. The test is similar to an ultrasound in that images are generated from outside your body. You still need to cleanse your bowels the night before. One disadvantage is that if the test reveals abnormalities, you will probably have to undergo a conventional colonoscopy to deal with it. Recent studies suggest that the virtual colonoscopy is as accurate as the regular colonoscopy.

Doctors recommend that everyone aged 50 and older undergo a colonoscopy and repeat the procedure every 10 years, if the test shows no abnormalities.

But if you're in the higher risk group, it's recommended you go for your first colonoscopy at age 40. The Canadian Cancer Society recommends that men and women age 50 and over have a fecal occult blood test at least every two years. FOBT blood testing helps identify polyps early before they become cancerous.

How is colon cancer treated?

If you require more treatment than just removing polyps, you could be facing:

• Surgery: the extent of surgery depends on the location and size of the tumour. A surgeon may remove part of your bowel. It is often possible to reconnect the bowel, but if it is not, you will need to undergo a colostomy, where the colon is brought out to the skin of the abdomen.
• Radiation therapy: high-energy X-rays are used to destroy cancer cells. It's not used often in cases of colorectal cancer because it is difficult to target specific parts of the bowel.
• Chemotherapy: this is used to reduce the likelihood of the disease spreading, to shrink tumour size or slow the growth of tumours. If surgery is not feasible, chemotherapy may be the only treatment.

What's the prognosis?

If colorectal cancer is detected in its early stages, it can be very treatable. Survival rates for early-stage detection are about five times higher than for late-stage cancers. In Canada, one in 27 men are likely to die from colorectal cancer. For women, the rate is one in 31.