Non-Invasive Tool Detects Colon Cancer

Colorectal cancer is the second-largest cancer killer in America. About 56,000 people die from it each year, but the vast majority of cases could be prevented with early screening.

The best screening test is a colonoscopy, in which doctors insert a camera through the rectum and into the intestines. But a recent ABCNEWS poll found that more than half of Americans 50 and over have never had the test.

Mike Blake of Rochester, Minn., is a prime example. Blake, 60, was scheduled to have a routine colonoscopy earlier this year. But he grew nervous and canceled. Two more times the colonoscopy was scheduled; and two more times Blake canceled.

"If you are going to get some kind of anesthesia, you figure it must be serious enough or painful enough, that it's something you don't want to do," he told ABCNEWS.

But recently Blake was ready to try what may be the next best thing: a "virtual" colonoscopy. No tubes and wires passing through his intestines. Instead, X-rays called "CAT scans" peer inside his body.

"This is a very thorough exam," said Dr. Dan Johnson, a radiologist at the Mayo Clinic who performed the screening test on Blake. "[It] allows us to look at the whole colon and rectum. … Not only the lining of the colon but we can actually look at the colon wall and structures outside the colon."

Same Pre-Exam Preparation Needed

Like traditional colonoscopy, virtual colonoscopy still required Blake to drink a preparation the night before to clean out his intestines.

The next morning, for the actual exam, Blake was placed on a table. Air was pumped through the rectum into his colon, expanding it for a better view. No sedation is required, but it can be uncomfortable.

Blake complained he felt stomach cramps during the screening.

Within 10 minutes the procedure was over. Blake then waited as his doctor scanned more than 700 images of his colon, representing more than four feet of his intestines, looking for tumors, or polyps that can turn into tumors.

"We transfer the data to the work station," said Johnson. "Then I examine the colon on the computer rather that on the patient.

"We can create a whole series of images any way we want. We call look at the colon in cross-section like we're slicing a loaf of bread, either in the short axis or the long axis."

If Polyp Detected, Scope Must Still Remove It

Virtual colonoscopy is considered experimental and the $500-$1,000 cost is not covered by insurance. Some preliminary data suggest it can detect 70 to 90 percent of polyps a half-inch or larger, which is less than traditional colonoscopy.

And if a polyp is discovered, as it is in about 10 percent of screenings, patients must still have a traditional colonoscopy, using a four-foot long scope, to actually remove it.

That is what happened to Blake.

"We were able to quite easily identify a couple of polyps in the second-lowest segment of the colon," said Johnson. Blake was sent to have the kind of traditional colonoscopy he had long shunned. But Blake was no longer complaining.

"I never would have done traditional colonoscopy if I didn't have to," he said. "I would have found reasons to put it off. The virtual colonoscopy made me willing to do it."

Virtual colonoscopy, while not as reliable as the real thing, can still be a valuable screening tool for many anxious patients.