Although the dreaded bowel cleansing routine is still required for virtual colonoscopy, the American Cancer Society’s (ACS; Atlanta) new guidelines for colorectal cancer screening now include computed tomography colonoscopy (CTC), a 15-minute test that does not require sedation, invasive scopes or recovery time. The addition of this test to the ACS’ guidelines is an effort to encourage more people to do colon cancer screening to avoid what has become the second leading cause of cancer death in the U.S.

Both CTC and stool DNA testing (Medical Device Daily, March 10, 2008) were added to the ACS’ screening guidelines, which were developed in collaboration with the U.S. Multi Society Task Force on Colorectal Cancer and the American College of Radiology (Reston, Virginia).

“There is finally, over the last four to five years, enough accumulated evidence supporting the ability of CTC to detect both colon polyps and cancers at a high rate,” Durado Brooks, MD, ACS’ director, Prostate and Colorectal Cancer, Cancer Control Science Department, told Medical Device Daily.

According to the ACS, half of all Americans who should be getting screened for colon cancer are not. Although traditional colonoscopy is the preferred screening strategy for colorectal cancer, CTC and stool tests may encourage hesitant patients to be screened. However, if one of those tests reveals a suspicious site, a colonoscopy would still have to be performed.

Each year nearly 150,000 people are diagnosed with colon cancer and almost 50,000 die from the disease annually in the U.S., many of which could be prevented with earlier detection. The five-year relative survival rate for people whose colon cancer is treated in an early stage is greater than 90%. But only 39% of colon cancers are found at that early stage. Once the cancer has spread to nearby organs or lymph nodes, the five-year relative survival rate decreases dramatically.

Until insurers and Medicare implement reimbursement strategies in line with the new guidelines, adoption of the test may be slow.

“Medicare reimbursement for traditional colonoscopy is significantly lower than what is charged by most colonoscopy facilities,” Brooks said. “If you talk with patients, particularly those outside of the Medicare system, the charges vary wildly so it’s difficult to put an average cost on colonoscopy. With CTC, it’s further complicated because up to this point almost no insurers pay for it as a screening tool.”

There’s also the question of qualified CTC providers. Although there are no statistics on how widely available CTC is, Brooks said he believes it’s readily available beyond just academic research centers.

“One of the points we went to great pains to make is the importance of a number of different quality factors in having a CTC as a primary method of screening.” Brooks said. “It requires that a certain level of equipment is available. The American College of Radiology has over the last few years developed a number of different quality standards and provides a training center for their membership. While overall access to high quality CTC is somewhat limited, over the next few years you’re likely to see an expansion in availability.”

Brooks said the test is done with high performance CT scanners with 16-slice capability and, “Most, if not all, radiologists will want to have very good standard 2-D and 3-D software systems to perform CTC,” he said.

Multidetector CT permits image acquisition of 1 mm to 2 mm slices of the entire large intestine well within breath-hold imaging times. Computer imaging graphics allow for visualization of 3-D endoscopic flight paths through the inside of the colon, which are simultaneously viewed with interactive 2-D images. The integrated use of the 3-D and 2-D techniques allows for ease of polyp detection, as well as characterization of lesion density and location.

“This is state-of-the art CT scanning,” Brooks said. “Anyone who has bought a new scanner in the last two to three years has the necessary equipment. Facilities with equipment that’s 10 years or older will need to update in order to do virtual colonoscopies,” Brooks said.

Virtual colonoscopy is somewhat of a misnomer. “One of the misunderstandings in talking with some patients is the perception that they just walk in and get an x-ray,” Brooks said, adding that bowel preparation is require and a tube must be inserted in the rectum about two inches in order to deliver room air or carbon dioxide. The purpose is to expand the colon so the entire diameter can be viewed during the CTC.

A study last fall comparing CTC with traditional optical colonoscopy found that the tests yielded similar results (MDD, Oct. 18, 2007).

The study, published in the New England Journal of Medicine, concluded that “primary CTC and OC screening strategies resulted in similar detection rates for advanced neoplasia, although the numbers of polypectomies and complications were considerably smaller in the CTC group.”