January 08, 2009

CT colonography a new alternative to colonoscopy

Written by
Rate this item
(0 votes)
A new, noninvasive virtual colonoscopy program to screen for colorectal cancer will be available at UAB beginning as early as April 1.

A new, noninvasive virtual colonoscopy program to screen for colorectal cancer will be available at UAB beginning as early as April 1, giving patients an effective, safe and well-tolerated option to traditional colonoscopy.

Cheri Canon, M.D., says CT colonography is a safe and effective way to identify early cancers.
CT colonography combines multi-detector CT with sophisticated post-processing software to obtain an interior view of the colon that otherwise is seen only with a more invasive procedure in which an endoscope is inserted into the rectum. The procedure is a promising method for detecting colorectal polyps and cancers, says Cheri L. Canon, M.D., associate professor in radiology.

“The important fact about colorectal cancer is that it is completely preventable,” Canon says. “With CT colonography, we are able to identify not only an early cancer, but pre-cancerous lesions. We’re diagnosing polyps up to 10 years before they become malignant. That’s huge, and it’s different than a mammography, for example, where we’re diagnosing early cancers and treating them. That’s why this is an important imaging breakthrough.”

Colorectal cancer is the third most common cancer and the second leading cause of cancer-related deaths in the United States according to the National Cancer Institute. It is estimated that 148,810 men and women will be diagnosed with the disease, and 49,960 men and women will die of cancer of the colon this year. From 2001-2005, the median age at diagnosis for cancer of the colon and rectum was 71, and the median age at death was 75.

A National Cancer Institute-funded study published recently in the New England Journal of Medicine found that CT colonography identified nine of 10 patients with significant (measuring 10 mm or greater) adenomas and cancers, proving comparable to conventional optical colonoscopy.
Currently, less than half of the population that needs to have their colon screened does so, and Canon believes the CT colonography may make it easier for those who fear colonoscopy now to be screened.

“People above the age of 50 should be screened every five to 10 years, depending upon the screening method,” Canon says. “Why is this not happening? Some of it is lack of information, but the main thing is many do not want their colon looked at. It’s uncomfortable; for some people it’s embarrassing. Research shows the CT colonography is a good alternative as it is well tolerated, less invasive and quick.”

Quick, easy exam
During a traditional colonoscopy, a colonoscope — a long, flexible tube — is inserted into the rectum. A tiny video camera at its tip enables the doctor to view the inside of the colon. In some cases, if a polyp or abnormal tissue is found, the doctor may remove it at that time. Alternatively, a biopsy of the polyp may be taken for lab analysis to determine whether subsequent surgical removal of the tissue is needed. Patients undergo the procedure under some form of sedation administered intravenously to minimize any discomfort.

With a CT colonography, patients have a small, soft-tip catheter connected to a CO2 inflator inserted into their rectum. The colon is inflated with CO2, and the physician then scans through the abdomen and pelvis twice and the procedure is done.

“It’s a pretty quick and easy exam, with the actual CT scan time taking about 30 seconds, and total exam time is less than 15 minutes,” Canon says. “And when you’re done, you’re done. You don’t have to recover from sedation like a traditional colonoscopy, and you can return to work immediately.”

Researchers believe CT colonographies will reduce the number of diagnostic colonoscopies. Most patients examined with a traditional colonoscopy do not have polyps and can be spared having to undergo the procedure. In fact, only 8 percent of the 2,600 patients screened as part of a recent NCI study on CT colonography needed to have an optical colonoscopy. This has been reproduced in other large trials, as well.

“That’s that saying most of the population that needs to be screened does not need to undergo endoscopy,” Canon says.

Canon hopes that when CT colonographies locate polyps or lesions patients will be taken to gastroenterology the same day to have them removed, thus avoiding a second bowel prep. “That’s going to take a lot of administrative maneuvering, but that’s what we want to move to eventually,” he says.

The CT colonography also has a lower risk of perforating the colon than conventional colonoscopy — another factor more attractive to patients.

Bowel preparations for a CT colonography are the same as they would be for a colonoscopy or barium enema examination. This means not taking iron pills or medications containing iron and taking bowel cathartics prescribed by the doctor. Patients also only can drink clear nonalcoholic liquids and eat soft foods, including Jell-O.

Extensively trained staff
UAB Radiology will use two cutting-edge CT scanners to perform the tests. Because the equipment and software are expensive, CT colonographies likely won’t be available at all local hospitals. UAB radiologists have undergone broad training on CT colonography and interpreting tests results.

“We’re fortunate because we have a staff of our abdominal imagers that has been extensively trained,” Canon says. “We’re going to double-read each case and compare it to the endoscopy results, if those are available, so the labor involved in reading these tests is quite extensive.”

Canon says radiology will begin performing CT colonography in patients with failed conventional colonoscopy in January; they will do the procedure on the same day so an additional bowel preparation can be avoided. The plan is to provide physician-referred screening service for a fee in late January.

Most insurers do not yet cover CT-based colonoscopies, but Medicare says it will make its decision on coverage in the next six months. The hope is there will be universal insurance coverage as early as April. Other insurers are expected to follow Medicare’s lead. The prospects for coverage appear good because of the safety and cost-effectiveness of the procedure, Canon says.

Scheduling for the procedure will be through The Kirklin Clinic radiology department at 731-9380. Those interested will be placed on a waiting list and scheduled when the procedure is available.

Read 1323 times Last modified on November 02, 2012