Technology choices in colorectal cancer

Did you know that every 9.3 minutes someone in America dies from colorectal cancer?

 

Cancer that occurs in the colon or rectum, is the second leading cause of cancer death in the United States, claiming over 53,000 lives in 2004.¹

 

This cancer isn't very choosy. Nearly everyone over 50 (45 for African Americans), male and female, is at risk of developing colorectal cancer. But it doesn't have to be that way.

 

A critical look at growths

Technology is helping doctors look for suspicious growths on the wall of the colon.

 

Growths that come in the form of mushroom shaped polyps or disc shaped flat lesions are known to be precursors to the most common forms of colon cancer.

 

Most of these growths are benign and may never become cancer. Removing the larger ones (>6mm), however, prevents them from transforming into cancer.

 

For most people, this strategy has proven to be a highly effective way to prevent colorectal cancer.

 

Revised guidelines
The American Cancer Society recently revised its guidelines on Colorectal Cancer prevention. For the first time, it introduced a clear distinction between the stool tests that detect cancer - once you've got it - and the imaging tests that are capable of detecting the precancerous growths.

 

Precancerous polyps are slow growing so the current guidelines suggest looking for them every 5 to 10 years using colonoscopy¹. According to a recent article in the Journal of the American Medical Association², the flat lesions - previously thought to be less important - may be about 10 times more likely to become cancerous than the polyps. (Fortunately, they are also rarer, occurring in only 6-15% of patients who have growths.)

 

4 available tests
According to the American Cancer Society, there are 4 kinds of imaging tests that can be used to find both cancer and precancerous growths.

• Double-contrast barium enema
• The sigmoidoscope
• Optical colonoscopy
• Virtual colonoscopy

 

A double-contrast barium enema (DCBE) is an X-ray technique that takes images of the entire colon. The x-rays are taken after the patient is given an enema with a barium solution and air is introduced into the colon.

 

It is less commonly used and is generally accepted to be less effective at detecting small, precancerous polyps. It's usually used only when it's not possible to use one of the other 3 kinds of tests.

 

The sigmoidoscope and optical colonoscopy require the use of an endoscope. An endoscope is a flexible tube with a camera on the end which can be inserted into the bowel to show the doctor a clear view of the lining of the colon.

 

The sigmoidoscope (which is less commonly used) uses a short endoscope and as such, can only look at the last part of the colon.

 

The optical colonoscope is more sophisticated and uses a longer flexible tube. Not only can it see the whole colon, but can simply and safely remove any polyps that are found. The fourth test offers physicians a virtual view of the colon - without the use of endoscopes.

 

A virtual alternative
Virtual or "CT" colonoscopy is a new technique. Instead of an endoscope, it uses a CT scanner to perform a short scan of the colon which a computer can then display as 3D images.

 

This 3D view makes it easier for the doctor to take more time to examine the "virtual" colon. And because the data can be stored in a computer, the 'virtual' colon can be reexamined at a later date.

 

Techniques for using virtual colonoscopy are still evolving, but a large national multi-site study³ has shown that virtual colonoscopy is effective at finding polyps larger than 5 millimeters in size.  One leading researcher has shown that polyps less than 6 millimeters can be safely left alone⁴ possibly avoiding the need for surgery.

 

'Virtually' - no sedation
The American Cancer Society points out an advantage to virtual colonoscopy is that sedation is generally not necessary.

 

Optical colonoscopy usually requires the patient to be sedated, which means they need to have someone drive them home after the procedure. With virtual colonoscopy a sedative isn't required.

 

Of course, if the virtual colonoscopy reveals you are one of the 10% of people in which growths are found, you will still need to have a sedative in order to have the growths removed through an optical colonoscope. The majorities of adults, however, have no growths and should be able to work immediately after the virtual colonoscopy procedure.

 

Although we've focused on imaging techniques to image cancerous and precancerous growths, you should not ignore the annual stool tests which can flag the need for further exams. To find out more visit the ACS website. Read on in this issue for stories about individual experiences with Virtual Colonoscopy and more information about this procedure.

 

 

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References:

 

1. U.S. Cancer Statistics Working Group. United States Cancer Statistics: 2004 Incidence and Mortality. Atlanta (GA): Department of Health and Human Services, Centers for Disease Control and Prevention, and National Cancer Institute; 2007.

 

2. Soetikno RM, Kaltenbach T, Rouse RV; et al. Prevalence of nonpolypoid (flat and depressed) colorectal neoplasms in asymptomatic and symptomatic adults. JAMA. 2008;299(9):1027-1035

 

3. ACRIN #6664 - The National CT Colonography Trial, C. Daniel Johnson et al - In Press

 

4. AJR Am J Roentgenol. 2008 Jan;190(1):136-44 Small and diminutive polyps detected at screening CT colonography: a decision analysis for referral to colonoscopy. Pickhardt PJ, Hassan C, Laghi A, Zullo A, Kim DH, Iafrate F, Morini S.

 

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- June 2008

 

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