"New test offers hope for easier colon screening" May 15, 2012|Deborah Kotz, Globe Staff
A
new method of performing virtual colonoscopy using a CT scan - which
does not involve the dreaded laxative preparation to clear the colon the
night before - may be about as effective as a standard colonoscopy at
identifying the large polyps most likely to become cancerous, according
to research conducted at Massachusetts General Hospital, Brigham and
Women’s Hospital, and elsewhere.
If larger studies confirm the
finding, the technique could eventually serve as a first-line screening
tool for colon cancer, especially for the many people who avoid
screening altogether.
The
new technique works by using a contrast agent - a tiny amount of dye is
ingested two days before the test - to highlight fecal matter in the
colon, which can then be digitally erased from the scan using a software
program, making it easier to see polyps.
In the study of 605
patients, published Monday in the Annals of Internal Medicine, the
virtual colonoscopy was able to identify more than 90 percent of
suspicious polyps that were 10 millimeters or larger, compared with 95
percent identified when the same patients later had a standard
colonoscopy.
The research was partially funded by GE Healthcare, maker of the CT imaging device.
“Study
participants reported an improved level of comfort with the new
technique,’’ said study author Dr. Michael Zalis, a radiologist at
Massachusetts General Hospital, primarily because it did not involve the
diarrhea-inducing prep that keeps most people in close range of a
bathroom the night before a colonoscopy....
Virtual
colonoscopy, with or without prep, has limitations. One in five
patients must undergo a standard colonoscopy after the imaging to have
suspicious polyps snipped off and biopsied. The CT scan also delivers a
dose of radiation that while only one-fifth of the dose of an abdominal
CT scan was significant enough to raise red flags at the US Preventive
Services Task Force.
Related: 21st-Century Operating Room
The government advisory group decided in 2008
not to recommend the use of virtual colonoscopy, saying the evidence
was not sufficient to prove the benefits outweighed the harm, which
includes a dose of radiation with every screening. The scan also images
areas outside the colon, sometimes detecting lesions that warrant
further testing to ascertain whether they are cancerous. This can lead
to unnecessary procedures when the lesion turns out to be harmless....
Some choice.
Traditional
colonoscopy trumps the virtual test when it comes to detecting smaller
polyps of less than 10 millimeters. The new study found that virtual
colonoscopy detected 70 percent of polyps under 8 millimeters, compared
with 88 percent detected by a scope.
What is not clear is whether
missing smaller polyps will make a difference in terms of catching
growths before they turn into cancer.
--more--"
Also see: Cheaper exam found effective at cutting colon cancer risk
