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TUESDAY, June 16 (HealthDay News) - CT colonography, a less invasive option to colonoscopy, is an effective way to detect colon cancer in people who have an elevated risk of the disease because of family history or a personal history of colon polyps, new research has found.
However, the study, in the June 17 issue of the Journal of the American Medical Association, reports that CT colonography (also known as "virtual colonoscopy") is less effective at correctly identifying colon cancers in people who've had a positive fecal occult blood test (FOBT), which means they have blood in their stool. A positive FOBT is a strong indicator that cancer might be present.
"People should be aware that colorectal cancer is a preventable disease," said one of the study's authors, Dr. Cristiana Laudi, a senior clinical researcher in the departments of gastroenterology and radiology at the Institute for Cancer Research and Treatment in Candiolo, Turin, Italy. "Our data suggest that CT colonography may provide a valid screening test also in subjects at increased risk of colorectal cancer."
Laudi said the findings are particularly important because colonoscopy screenings tend to have low adherence rates, and a less invasive test might boost compliance rates.
The American Cancer Society already recommends CT colonography as an option for people who have an average risk of colorectal cancer, according to Dr. Durado Brooks, director of colorectal cancer for the society. And the study, he said, provides some evidence that CT colonography might also be useful in high-risk populations.
"The sensitivity for cancer was extremely high," Brooks said. But the test did miss some polyps, he added. And he cautioned that the findings need to be confirmed by others before any definitive recommendations can be made.
The study included 937 people who were considered at high risk for colorectal cancer because of a family history of the disease (373 people), a personal history of colon polyps (343 people) or a positive result on the FOBT (221 people). The participants were recruited from 11 medical centers in Italy and one in Belgium. They averaged 60 years old.
Each participant underwent CT colonography followed by colonoscopy on the same day. Preparation for CT colonography is usually the same as is used for colonoscopy, though Laudi said that a less potent laxative is sometimes used. But, the colon still needs to be emptied and clean for the CT test. Colonoscopy can be used to screen, diagnose and treat colorectal cancers, but it is considerably more invasive, carries a greater risk of complications and often requires sedation.
Overall, the virtual test found 85 percent of the colorectal cancers detected by colonoscopy. False-positive rates were 4 percent for advanced cancers and 15 percent for people with a positive FOBT.
"Virtual colonoscopy is a valid screening test for colorectal cancer, trading off a better acceptance and lesser invasiveness by comparison with colonoscopy, with the possibility of missing small polyps that may, however, not be so relevant in terms of risk of developing into cancer," Laudi said.
Because a positive FOBT indicates a strong likelihood of cancer and a need for treatment, Brooks said he wouldn't recommend CT colonography for people with a positive test unless there were some extraordinary individual circumstances that prevented the use of colonoscopy.
"The question remains whether clinicians are willing to accept a study with decreased sensitivity for the potential of increased adherence with recommended screening and surveillance guidelines," wrote Dr. Emily Finlayson from the University of Michigan, in an accompanying editorial in the same issue of the journal. "With the majority of individuals in the United States who meet the criteria for colorectal cancer screening and surveillance not undergoing recommended procedures, an imperfect test that has a lower risk profile and greater acceptance among patients seems to be an appealing solution."
However, people on Medicare or Medicaid currently do not have the option of CT colonography unless they're willing to pay out of pocket for the test. In May, the U.S. Centers for Medicare and Medicaid Services said that there was insufficient evidence to support the use of the test.
More information
The Radiological Society of North America has more on CT colonography.
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