Virtual Colonoscopy May Simplify Cancer Screening
An X-ray technique called virtual colonoscopy appears to be as effective as the conventional procedure for detecting polyps in the colon but is less invasive, does not require sedation and eliminates the risk of inadvertently puncturing the intestine, researchers said Monday.
The procedure does not eliminate the 24-hour cleansing in which wastes are washed out of the intestines -- a process many patients find the most objectionable part of the procedure. And a regular colonoscopy is required if polyps are detected.
Nonetheless, the virtual procedure minimizes the psychological barrier that prevents a majority of Americans from undergoing screening for colorectal cancer -- fear of having the long metal endoscope bearing a tiny TV camera inserted through their rectum and snaked through their intestines.
Colon cancer strikes an estimated 105,500 Americans each year and kills 57,000, making it the most deadly cancer after lung cancer. But the disease is highly curable if detected early, and the vast majority of those deaths could be avoided. However, only 37% of tumors are detected sufficiently early.
“Virtual colonoscopy is an accurate screening tool ... and this hopefully will lead to more widespread screening,” said Dr. Perry J. Pickhardt of the University of Wisconsin Medical School. “If we can screen more patients, we know it will prevent cancers and save lives.”
Pickhardt presented his findings Monday at a Chicago meeting of the Radiological Society of North America. They will be published this week in the New England Journal of Medicine.
In an editorial in the journal, Dr. Thomas Lamont of the Beth Israel Deaconess Medical Center in Boston suggested that the technique may be “ready for prime time.”
Virtual colonoscopy uses a CT scanner to produce images of the intestines, enabling researchers to identify polyps, which are frequently precursors of tumors. Smaller studies have produced mixed results.
Pickhardt and his colleagues refined the technique, using new software that produced a three-dimensional image rather than the two-dimensional one achieved in previous studies.
The team studied 1,233 adults, subjecting patients to both conventional and virtual colonoscopies. They found that the virtual technique detected about 92% of polyps large enough to be a potential problem, while conventional colonoscopy detected about 89%.
Surprisingly, 54% of the patients found the virtual colonoscopy to be more uncomfortable, probably because air is pumped into the intestines to inflate them slightly, allowing better viewing. Air is also pumped in during a conventional procedure, but patients are sedated.
But that sedation carries its own problems. Patients can’t drive afterward, so someone must bring them to the diagnostic center, and they generally require at least a couple of hours for recovery. With virtual colonoscopy “there’s no recovery time,” Pickhardt said.
Virtually everyone agrees that further studies are necessary to confirm Pickhardt’s results, especially to show that similar accuracy can be obtained by radiologists at community hospitals. Pending those studies, the American Cancer Society will continue to recommend conventional colonoscopy, said the society’s Dr. Herman Kattlove.
