What is colorectal cancer?

Colorectal cancer is the development of cancerous cells of the large intestine usually arising from polyps.  Polyps are growths of the colon ranging in size from a grain of rice to golf ball size.  There are various types of polyps that usually take 3-10 years to grow to significant size.

What causes colorectal cancer?

The exact causes are unknown, but appear to be both due to inherited and lifestyle factors.  Diets high in fat and low in fruits and vegetables may increase the risk.  Cigarette smoking, sedentary lifestyle and obesity increase the risk.  Genetic factors may determine a person’s susceptibility, whereas diet and lifestyle may determine who actually goes on to develop cancer.

How common is colorectal cancer?

It is the second leading cause of cancer deaths and the third most common cancer overall.  More women over the age of 75 die of colorectal cancer than from breast cancer.  

Who is at risk?

Anyone over age 50 is at increased risk.  People with a family history are also at increased risk.  Persons with two or more first degree relatives or any first degree relative diagnosed with colon cancer under age 60 carry a risk 3-6 times greater than the general population.  A single first degree relative diagnosed at age 60 or older carries a risk 2 times the general population.  Anyone with a personal history of colon cancer or polyps at any age, or endometrial (uterus) or ovarian cancer before age 50, is also higher risk.  Women with a history of breast cancer have only a slightly higher risk.   

What are the symptoms of colorectal cancer?

Colon cancer usually does not cause symptoms until the advanced stages, therefore screening is recommended even if asymptomatic.  Change in bowel habits, rectal bleeding, anemia, weight loss, and abdominal pain can be associated and should be brought to your doctor’s attention.  

How can you prevent colorectal cancer?

Screening is most important and has been shown to save lives.  Average risk patients start at age 50.  High risk patients should start at age 40 and even as early as age 20 in special circumstances.  Regular aspirin and other non-steroidal drug use have shown to prevent polyps and reduce cancer deaths, but due to increase risk of bleeding should be used with your doctor’s guidance.  Other dietary supplements such as folate, calcium, vitamin D and low fat diet have been shown to be beneficial.  High fiber, smoking cessation and exercise are helpful as well.

What tests are available for screening?

1. Fecal occult blood test (FOBT).  Microscopic blood is tested on stool cards.  If positive, a colonoscopy should be performed.  It is the least sensitive and specific test available.  It should be performed annually.
2. Stool DNA.  Stool is checked for DNA changes that are associated with polyps and cancer.  It is non-invasive and more sensitive and specific than FOBT but more expensive.  It should be performed annually.
3. Sigmoidoscopy and double contrast barium enema (DCBE).  Sigmoidoscopy is a flexible video scope inserted in the colon used to look at a third of the colon.  It is combined with DCBE, which is liquid barium plus air injected to examine the entire colon.  If polyps are seen, colonoscopy is recommended.  It is more useful than stool tests but has limited sensitivity.  Large polyps are often missed.  It should be performed every 5 years.
4. Colonoscopy.  The current gold standard for screening as well as treatment for polyps and cancer prevention.  Colonoscopy is a flexible video scope that examines the entire colon.  It is currently the most sensitive and specific.  Polyps found are removed at the same time, thus preventing cancer.  It is usually repeated every 10 years if average risk and no polyps found, versus 3-5 years if polyps found.  High risk patients may be screened at even earlier intervals.
5. CT colonography or virtual colonoscopy.  A new technique that uses x-rays to search for polyps.  It requires a bowel cleansing and injection of air into the colon for adequate visualization.  Sedation is not used.  If polyps are found a colonoscopy is recommended.  It is fairly adept at picking up large polyps, although small polyps are often missed.  Insurance coverage currently is variable.

What is involved with colonoscopy?

Colonoscopy involves a bowel prep for cleansing to achieve adequate visualization.  Clear liquids only are required the day prior, in addition to a liquid laxative usually taken the evening before.  The end result is diarrhea which is the most common discomfort.  The procedure itself is well tolerated.  An IV is placed and medicines are given for sedation and pain.  Most patients are in a twilight sleep, napping through the procedure to wake up and remember nothing.  While sedated, the colonoscope is inserted into the colon.  Air is insufflated to expand the walls.  The scope is advanced throughout the entire colon.  Polyps are removed with forcep biopsies or snared and burned off.  Polyps are examined under the microscope to check for cancer.  The procedure takes 15-20 minutes to complete.  After a recovery period you are discharged home.  A driver is required secondary to the sedation.  Risks involved with the procedure are extremely rare and include bleeding, perforation, infection, reaction to the medicine and even more rare death.  The benefits of screening far outweigh the risks.