Colon cancer test may not require laxatives: study

People getting checked for signs of colon cancer may not need to take a laxative if they choose a CT scan for their cancer screening over a tradition colonoscopy, according to a new study.

The findings suggest a so-called CT colonography is almost as good at identifying certain polyps as a traditional colonoscopy, and researchers said eliminating the need for laxatives may encourage more people to get screened.

"The results of this study open the door to a more patient-friendly screening," said Dr. Michael Zalis, the study's lead author and director of CT colonography in the department of imaging at Massachusetts General Hospital in Boston.

Zalis added, however, that CT colonography is not yet covered by government insurance programs - like Medicare and Medicaid - and more research is needed before people switch to a laxative-free method of screening.

In traditional colonoscopy, a doctor uses a camera called an endoscope to look for signs of cancer within the colon and rectum. The procedure usually requires sedation.

During a CT colonography, the colon is filled with a gas and the patient is told to hold their breath while images are taken.

For both tests, patients typically take a laxative the night before the screening to eliminate any digested food that might be in the colon.

Zalis and his colleagues wanted to test whether or not a CT colonography remained accurate even when the patient did not use a laxative. Instead, people were told to reduce their fiber intake and periodically drink liquids with an added substance that tags the feces in a person's colon.

After the images are taken, a computer program - like software invented by Zalis and two of his coauthors - removes the feces from the picture, which leaves an empty colon and any polyps.

Between June 2005 and October 2010, Zalis and his fellow researchers recruited 605 people - all between 50 to 85 years old and at average risk of colon cancer - for their study.

Each person underwent a laxative-free CT colonography and then a traditional colonoscopy about five weeks later.

Overall, the laxative-free method identified 91 percent of polyps one centimeter or larger, compared to 95 percent with traditional colonoscopy. The difference between the two, according to the researchers, could have been due to chance.

That wasn't the case for smaller polyps, however. The researchers found that a traditional colonoscopy was better at identifying polyps under a centimeter in size, compared to the laxative-free CT colonography.

ADVANTAGES AND DISADVANTAGES

Colonography "does have some advantages and disadvantages and I think it's important for people to know what those are," said Dr. Perry Pickhardt, of the department of radiology at the University of Wisconsin School of Medicine and Public Health in Madison.