CT Colonography next in Colon Screening

Researchers have come up with yet another screening test for colon cancer that is gaining in popularity among patients especially. This noninvasive test involves dye inserted into the rectum and a CT scan of the abdomen to outline any polyps or colon cancer that might be there. It takes an average of 175 studies for a new radiologist and radiological technician to become technically

savvy enough to perform the test.

In the beginning, insurance companies used to refuse payment for CT colonography, citing the idea that they were less effective than colonoscopies and more expensive than colonoscopies to do. Unfortunately, this meant that patients who wanted a CT colonography had to pay out of pocket for the procedure. Now, as the procedure is gaining acceptance, more insurance companies are paying for CT colonography and more patients are having the procedure in lieu of colonoscopy. The potential for increased compliance is much greater than with colonoscopy.

The initial concern was that CT colonography was too hard for most radiologists to learn with an accuracy rate that rivaled colonoscopy. The new study out showed that novice readers needed to read about 175 studies, as mentioned above, in order to find larger polyps, of the size greater than 10 mm. Going through continuing education before reading these examinations seemed to make a difference in how many colonography tests it took to become proficient in reading them. In the first fifty exams read, about 76 percent of doctors were able to read colonography examinations to the level of 6 mm or larger. This compared to 91 percent for those who read up to 200 CT colonography examinations. For 10 mm polyps or larger, the number was 96 percent accuracy for 200 CT colonography examinations read.

Overall, for those who actually had cancer of the colon, the accuracy rate was 91 percent, practically independent of how many scans had been read. Overall, the sensitivity of CT colonography was consistent with that of colonoscopy, making as good a test for colon problems and colon cancer as colonoscopy.

Before the study, researchers determined that you needed 95 percent accuracy to lesions 10 mm or larger and 90 percent accuracy to lesions bigger than 6 mm in order to be a test that was just as good as colonoscopy. It was found that trainees reached this level after reading an average of 164 tests. Extra training didn’t seem to make a big difference in the ability to read the test accurately and sensitively.

What this means is that it helps to ask the doctor doing the test how many CT colonography tests they have read in the past and, if the number is higher than around 175, you can trust that the reading you get will be as accurate as if you had a colonoscopy.