Vital: Make sure yours are done right

Colorectal cancer is the second deadliest cancer in the US, accounting for 50,000 deaths each year — yet it can usually be prevented through regular colon screenings. Still, half of all Americans aren’t getting screened. To learn more about colorectal cancer detection and prevention, Bottom Line/Retirement spoke with Robert Smith, PhD, director of screening for the American Cancer Society…

Why is regular colon screening so important?

Most colorectal cancers begin as precancerous polyps, or lesions, that take years to turn into full-blown cancer. Regular screening can detect precancerous polyps and cancerous tumors in the early stages, allowing doctors to remove them before they turn dangerous.

What are the basic screening recommendations?

Regular screening can detect cancer early, when treatment is very successful, and can detect precancerous polyps, which can be removed before they become cancer. People at average risk should begin screening at age 50 with either stool tests or colonoscopy. Stool tests, which must be done every year, primarily are effective at detecting cancer, while colonoscopy, which should be done every 10 years, can detect cancer as well as precancerous polyps. People with a personal history of precancerous polyps or inflammatory bowel disease should get a colonoscopy every three to five years. And those who have a family history of colorectal cancer or precancerous polyps should get their first colonoscopy at age 40 and another every five years thereafter. If cancer is suspected, a variety of stool tests can also be done.

The American Cancer Society recently endorsed CT colonography. Why?

We now have evidence that a CT scan of the colon — also referred to as a virtual colonoscopy — is as good as a standard colonoscopy at detecting polyps. And since a CT scan is noninvasive (unlike a colonoscopy), this option should encourage more people to get screened. You will still have to “prep,” and if something suspicious is found, you will need to undergo a regular colonoscopy. Some facilities offer same-day colonoscopy for individuals who have a positive CT colonography, which prevents having to do a second prep. However, this requires coordination between the radiology and gastroenterology departments. If the facility you use is not able to do this kind of coordination, then you’ll have to schedule the colonoscopy separately and do the prep again.

Don’t CT scans of the colon often miss “flat” lesions? Is this a concern?

The results of the study that made this claim, which was conducted at a veteran’s hospital in San Diego, have been widely misinterpreted. Much of the confusion is because the term “flat lesions” actually describes two very different types of polyps. The more common type is identical to normal polyps, except that the lesions are wider than they are high — which is why they are called “flat.” These lesions are no more dangerous than ordinary polyps, and are detected quite easily by regular colonoscopies and CT scans.

The other type of lesion really is flat, or even depressed. These are rare, and typically occur in someone with a history of advanced polyps or colorectal cancer — in which case the doctor will already be on the lookout for them. It’s true that they are more likely to develop into cancer and tougher to spot. To see them, a doctor will need to do an especially careful colonoscopy, perhaps in conjunction with other techniques, such as chromoendoscopy (where a dye is sprayed in the colon to highlight any lesions). That said, there’s always a chance that a small lesion will simply escape detection.

How can you be sure that your doctor is proficient at colon scans?

There probably is a range of skill and attentiveness when it comes to administering colon scans. Frankly, the public is at a disadvantage here, since there’s no way to evaluate the quality of the screening. In general, I would say your safest bet is to get your colon scanned at a facility that does a high volume of colon testing — that is, thousands of colon scans per year. As a patient, you can also help ensure a high-quality scan by carefully following all bowel-cleansing instructions beforehand.

Does diet play a role in colorectal cancer?

Diets high in beef, pork, lamb or grilled or processed meats have been strongly linked to increased risk for colorectal cancer, while a diet high in vegetables and fruits has been linked to a decreased risk. Other risk factors include physical inactivity, obesity, smoking, heavy alcohol use and type 2 diabetes. If you have any of these other risk factors, be sure to keep up with regular screenings.


Pros and cons of various types of colon screenings…

Flexible sigmoidoscopy. The doctor looks at the last two feet of the colon using a flexible tube with a camera on the end.

Pros: Takes 10 to 20 minutes… minimal bowel prep required… sedation usually not used… specialist not required.

Cons: Has to be repeated every five years… examines only the one-third of the colon where about 65% of precancerous polyps are found… can’t remove all polyps… may cause discomfort… small risk of bleeding, infection or bowel tear… follow-up colonoscopy will be needed to check the rest of the colon if abnormalities are found.

Colonoscopy. The doctor looks at the entire colon using a longer version of the tube used in sigmoidoscopy.

Pros: Can usually view entire colon… doctor can remove polyps during the procedure and immediately have them biopsied… needs to be done only every 10 years in most cases… can diagnose other diseases, too — such as ulcerative colitis and Crohn’s disease.

Cons: Can miss small polyps… full bowel preparation needed… more expensive than other forms of testing… sedation usually needed… small risk of bleeding, bowel tears or infection.

Virtual colonoscopy. Also known as CT colonography. Air is pumped into the colon, and a CT-scanner is then used to take multiple images of the colon.

Pros: Noninvasive… takes only 10 minutes… can usually view entire colon… no sedation needed.

Cons: Needs to be repeated every five years… can miss small polyps… full bowel preparation needed… doctor can’t remove polyps during testing… follow-up colonoscopy will be needed if abnormalities are found.

Double-contrast barium enema. Barium sulfate and air are pumped into the colon, which is then X-rayed to look for abnormalities.

Pros: Noninvasive… can usually view entire colon… relatively safe… no sedation needed.

Cons: Needs to be repeated every five years… can miss small polyps… full bowel preparation needed… doctor can’t remove polyps during testing… follow-up colonoscopy will be needed if abnormalities are found.