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?
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?
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?
- 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.
- 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.
- 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.
- 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.
- 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.