By Andrew M. Seaman
NEW YORK Mon May 14, 2012 5:06pm EDT
NEW YORK (Reuters Health) - 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.
Pickhardt, who was not involved with the new study, told Reuters Health that some doctors may not be okay with relying on a test that only consistently finds larger polyps.
Although it may spot fewer small, pre-cancerous polyps, Zalis said CT colonography is still better than no screening -- and eliminating the laxative preparation may increase the number of people who get the test.
"The prep, it turns out, is highly objectionable to many people, and it deters people from getting screened," he said.
In his team's study, 290 people said they'd prefer a CT scan for screening in the future, and 175 picked the traditional colonoscopy.
"If this gets a few people through the door, it's worth it, but it shouldn't be our first option," said Pickhardt. "There is a downside; you're trading one thing for another."
Pickhardt said that at his center, the laxative-free method is usually reserved for frail, older patients who have a higher risk for complications.
Zalis said another benefit to CT colonography might be the cost. He said the scan could be done for about 30 percent of what a traditional colonoscopy costs -- between $400 and $700 -- by eliminating things like anesthesia.
In another recent article, researchers came up with a different way to reduce the unpleasantness of the standard laxative preparation by using a combination of the laxative MiraLAX and Gatorade.
That study, published in the American Journal of Gastroenterology, looked at a sample of 222 patients who took a single dose or split dose of Golytely, the traditional pre-colonoscopy laxative beverage, or the MiraLAX/Gatorade combination.
MiraLAX has to be paired with Gatorade or a similar drink, researchers said, because it flushes electrolytes from the body.
Overall, a split dose of the MiraLAX and Gatorade combination appeared to be an "effective, safe and tolerable" option for patients undergoing a traditional colonoscopy. The patients also said they tolerated it better than Golytely.
Dr. M. Mazen Jamal, the study's senior researcher from the department of gastroenterology at the Long Beach Veterans Affairs Healthcare system in California, said Golytely has been known to have unpleasant side effects like stomach aches, vomiting and nausea.
"I feel confident that this is a viable alternative for low-risk patients or for patients who could not tolerate Golytely," said Jamal.
As for when a person should be screened for colon cancer, the U.S. Preventive Services Task Force (USPSTF), a government-backed advisory group, recommends screening starting at age 50 in average-risk people, and typically stopping at age 75.
The USPSTF doesn't endorse any particular type of test over others. It recommends screening either with colonoscopy every 10 years, with another invasive test called a sigmoidoscopy every five years or using an annual at-home test called a fecal occult blood test.
Zalis's study was partially funded by the American Cancer Society and GE Healthcare.
SOURCE: bit.ly/JOLDrc Annals of Internal Medicine, online May 14, 2012 and bit.ly/JOLLGZ American Journal of Gastroenterology, online May 8, 2012.