New Screening Tool Could Increase The Use Of Virtual Colonoscopies

Colorectal cancer screening can cut a person’s risk of dying from the disease in half, yet about 40 percent of those who should get tested don’t do it.

One reason is that the “gold standard” for screening, an optical colonoscopy, requires a rigorous preparation to empty the colon, and it gives many people pause. A new method that doesn’t require patients to take laxatives to empty their bowel beforehand could boost screening rates. But some experts question whether it’s a good solution. 

During an optical colonoscopy, a doctor inserts a long tube with a lighted camera at the end into the anus and snakes it through the entire colon, looking for and removing tissue masses called polyps that may be cancerous or may become cancerous. 

The new test builds on another screening method often referred to as a virtual colonoscopy, the popular term for CT colonography. The virtual colonoscopy is non-invasive, but patients must still undergo bowel cleansing. They then have a CT scan, which generates three-dimensional images of the colon on a video screen for physicians to examine. 

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New Screening Tool Could Increase The Use Of Virtual Colonoscopies

In the new approach, patients drink a contrast dye a day or so before the procedure that “tags” the feces in their colon. The patient then has a virtual colonoscopy, and the feces can be identified and digitally removed from the CT image. No bowel cleansing is necessary. 

In a recent study published in the Annals of Internal Medicine, this laxative-free virtual colonoscopy was nearly as effective as the optical colonoscopy at detecting larger polyps of at least 10 millimeters that are responsible for most colorectal cancers.

“If somebody’s not getting screened, and it’s because of the prep, we can address this issue” with the laxative-free test, says Michael Zalis, director of CT colonography at Massachusetts General Hospital and the lead author of the study.  

The U.S. Preventive Services Task Force, a federal panel that evaluates medical evidence to promote effective prevention efforts, recommends that men and women get screened for colorectal cancer starting at age 50 and continue at intervals until age 75. It recommends one of three tests to screen for colorectal cancer: an optical colonoscopy once every 10 years; a sigmoidoscopy, which is similar to a colonoscopy but only examines the lower half of the colon, once every five years, or a fecal-occult blood test that looks for blood in the stool, once every year. 

Many people don’t get screened when they should. In 2010, 59 percent of people age 50 and older had been screened for colorectal cancer according to recommended guidelines, the American Cancer Society found.  In contrast, 76 percent of women age 18 and older had received Pap tests to screen for cervical cancer within the past three years, and 67 percent of women age 40 and older had mammograms in the prior two years. 

The Preventive Services Task Force, which says it has insufficient evidence, has not made a recommendation about virtual colonoscopy, in part because of concerns about exposing asymptomatic people to unnecessary radiation.  Another downside, experts note, is that other expert groups have recommended that the test must be repeated every five years, twice the frequency of an optical colonoscopy. 

The American Cancer Society evaluated the data and decided to recommend the virtual colonoscopy. “It does a good job at finding large polyps and cancers,” says Durado Brooks, the ACS’s director of prostate and colorectal cancers. ACS provided funding for the laxative-free test study, the results of which are promising, says Brooks, but need to be replicated on a broad scale.

Many clinicians say they support any effective method that increases the likelihood people will get screened. “The best test is the one that gets done,” says Joanne Schottinger, the assistant medical director for quality at Kaiser Permanente in Southern California. (Kaiser Health News is not affiliated with Kaiser Permanente.)

For the past several years, Kaiser Permanente has sent fecal immunochemical testing kits, a type of fecal occult test, to every KP member’s home who should be screened. Members use the kit to collect a stool sample and send it in a prepaid mailer to the lab, which evaluates whether there is blood in the sample. If the sample is positive, the member is advised to get a colonoscopy. 

In Southern California in 2010, 70 percent of privately insured Kaiser Permanente members in the target group for screening for colorectal cancer were tested, as were 84 percent of those on Medicare, says Schottinger. Those figures are significantly higher than the 59 percent nationwide who were up to date with screening in 2010. 

Sometimes ignorance of screening recommendations is as much a problem as avoidance. Tom Foeller was diagnosed with rectal cancer in 2006 after he asked his doctor to test him for colorectal cancer as part of a routine physical exam. 

Foeller, who was then a supervisor at a federal electrical power marketing agency in Portland, Ore., was thinking of buying a sailboat, he told his doctor, and he jokingly said he wanted to be sure he would live long enough to pay it off.  

His doctor did a fecal blood test, and immediately ordered a colonoscopy. The diagnosis: Stage 3 rectal cancer. Foeller had surgery, radiation and chemotherapy. He’s been cancer free for nearly six years.

Like many people, Foeller says he was unaware that he should have been screened for colorectal cancer at age 50. 

He wasn’t feeling ill, and his only symptom was occasional irregularity. Foeller thought to ask about colorectal cancer screening only because he had an acquaintance who had been diagnosed with the disease. His primary care doctor never brought it up. “He never mentioned it, much to my chagrin and subsequent problems,” says Foeller, “and I was ignorant not to ask for it when I should have.”

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