Virtual Colonoscopy Ready for Prime Time as Less
Worrisome Way to Find Colon Cancer
Large trial says CT Colonography comparable to
colonoscopy in helping prevent third most diagnosed cancer, second leading cause of cancer death
Virtual colonoscopy, a minimally invasive
procedure, produces 3-D images and videos of the lining of the rectum
and colon. The technique can detect precancerous and cancerous polyps.
Image courtesy of Dr. Perry J. Pickhardt, University of Wisconsin
Medical School.
Sept. 22, 2008 Medical researchers have long
sought an effective alternative to the standard colonoscopy, which uses
a long, flexible tube with a camera to view the lining of the colon to
detect cancer and precancerous polyps. Most have assumed it is the
procedure that causes millions of older men to skip the recommended exam
that could save them from colorectal cancer, the second leading cause of
cancer death. Researchers claim they have found the answer -
computerized tomographic (CT) colonography, known as virtual
colonoscopy, is now comparable to standard colonoscopy.
The virtual colonoscopy is almost as good at
detecting cancer and precancerous polyps and could serve as an initial
screening exam for colorectal cancer, according to the results of the
American College of Radiology Imaging Network (ACRIN) National CT
Colonography Trial.
The technique uses X-rays and computer-based
virtual reality technologies to produce 3-D images and videos of the
lining of the rectum and colon. Recent studies have suggested that CT
colonography can be nearly as accurate as conventional colonoscopy in
detecting clinically important large colorectal polyps, but questions
were raised about its ability to detect smaller polyps.
Cancer's precursor polyps, known as adenoma, sharply
increase after age 50
Below
story see...
Medicare's coverage of tests for colorectal cancer.
More about colon cancer.
Sept. 3, 2008 People over age 50, who are still
wrestling with the decision of whether they should have a colonoscopy,
received another wake-up call this week from a study detailing the rapid
increase of polyps the precursor of virtually all colorectal cancers
that begin to occur at that age.
Read more...
This new ACRIN clinical trial was sponsored by the
National Cancer Institute (NCI), part of the National Institutes of
Health (NIH). The study evaluated more than 2,500 patients, age 50 or
older, at 15 sites nationwide.
It is the largest multi-center study to compare the
accuracy of state-of-the-art CT colonography to the gold standard of
conventional colonoscopy. The results of this study are published in the
Sept. 18, 2008, issue of the New England Journal of Medicine.
Each participant had a CT colonography followed by
a standard colonoscopy, with 99% of both exams completed on the same
day. Both procedures require that patients adhere to a strict
bowel-cleansing process the day before, including laxatives and a
clear-liquid diet. As usual during standard colonoscopy, physicians
removed any suspicious polyps or tissues for further analysis.
The results, reported in the September 18, 2008,
issue of the New England Journal of Medicine, showed that nearly 300
patients had at least 1 precancerous or cancerous polyp measuring a
half-centimeter or more in diameter. About a third of these patients had
larger tumors, measuring at least 1 cm.
CT colonography identified about 90% of the
patients who had larger tumors detected by standard colonoscopy. As in
previous studies, the CT technique's sensitivity declined with smaller
tumors.
Overall, it identified about 65% of the patients
who had tumors measuring a half-centimeter or more detected by regular
colonoscopy.
Although the virtual scan is not as accurate as the
standard procedure, it may be more appealing for those put off by the
long tube and sedation used for standard colonoscopy.
"The most important advice we can give to patients
is to get screened," said study coauthor Dr. Paul Limburg of the Mayo
Clinic in Rochester, Minnesota. "How they get screened should be an
individual decision based upon discussions between patients and their
providers."
"CT colonography could be adopted into the
mainstream of clinical practice as a primary option for colorectal
cancer screening. We hope that this additional, less-invasive option for
cancer screening will lead more people to get screened and will
ultimately result in fewer deaths from colorectal cancer," said C.
Daniel Johnson, M.D., of the Mayo Clinic in Scottsdale, Ariz, and
principal investigator for the ACRIN National CT Colonography Trial.
Colorectal cancer is the third most frequently
diagnosed cancer and second leading cause of cancer death in men and
women in the United States. Although screening recommendations vary
somewhat, many recommend that adults aged 50 and older in the general
population receive a colonoscopy every 10 years or more frequently,
depending on known risk factors.
Yet, despite the known benefits of screening,
studies indicate that the majority of Americans age 50 and older are not
being screened for the disease.
"Imaging advances such as virtual colonoscopy are
an important step forward that could potentially increase the number of
people who would agree to be screened. We hope, through continued
imaging research and the development of molecular diagnostic techniques,
that we will continue to improve our screening options in the years
ahead and, as a result, continue to see a decline in the incidence of
colorectal cancer," said NCI Director John E. Niederhuber, M.D.
"Previous single-site studies had indicated that CT
colonography held promise in screening for colorectal cancer due to its
accuracy, safety, cost-effectiveness, and patient acceptability.
However, validation of the technique across multiple centers and
radiologists was needed to provide more evidence of the exams
viability. The ACRIN trial has now validated that CT colonography could
serve as an initial screening exam for the population in which screening
is indicated," said Mei-Hsiu Chen, Ph.D., trial statistician, ACRIN
Biostatistics and Data Management Center, Brown University, Providence,
R.I.
In the ACRIN trial, the CT colonography findings
were evaluated using standard colonoscopy as the reference standard. CT
colonography was found to be highly accurate for the detection of
intermediate and large polyps.
Ninety percent of the polyps 1 centimeter or larger
were detected by CT colonography. Even polyps as small as one half
centimeter were detected by CT colonography with a high degree of
accuracy.
Since most colon cancers develop from polyps, and
screening to find and remove these polyps can prevent colon cancer, an
opportunity exists to save lives with early detection.
"There are clearly clinical settings in which CT
colonography, colonoscopy, or both tests in combination offer distinct
advantages. The most important advice we can give to patients is to get
screened. How they get screened should be an individual decision based
upon discussions between patients and their providers," said
gastroenterologist and study author Paul Limburg, M.D., Mayo Clinic in
Rochester, Minn.
Study participants had to be at least 50 years old,
scheduled for a screening colonoscopy, and not have received a
colonoscopy in the past five years. Each participant had a CT
colonography followed by a colonoscopy, with 99 percent of both exams
accomplished on the same day.
Participants scheduled for a screening colonoscopy
were recruited with assistance from gastroenterologists at each
participating site. Preparation for CT colonography and colonoscopy both
involve taking solutions to clear and cleanse the colon.
Research advocates played an important role in
advising the scientists who conducted this study. "As the ACRIN patient
advocate who worked with the research team and as a research advocate
with C3: Colorectal Cancer Coalition, I am pleased that CT colonography
can be added to the list of screening options. Having a method that is
accurate and comprehensive while being minimally invasive is needed if
we are to succeed in substantially reducing deaths from colorectal
cancers," said Pam McAllister, Madison, Wis.
By National Institute of Diabetes and
Digestive and Kidney Diseases
Your colon, also known as the large intestine, is
part of your digestive system. It's a long, hollow tube at the end of
your digestive tract where your body makes and stores stool. Many
disorders affect the colon's ability to work properly. Some of these
include
>>
Diverticulitis - inflammation or infection of pouches in the colon
>>
Irritable bowel syndrome - an uncomfortable condition causing
abdominal cramping and other symptoms
Treatment for colonic diseases varies greatly
depending on the disease and its severity. Treatment may involve diet,
medicines and in some cases, surgery.
Editor's Notes:
ACRIN is a NCI Clinical Trials Cooperative Group.
It is made up of investigators from over 100 academic and
community-based medical facilities in the United States and several
international institutions. ACRINs mission is to develop information,
through clinical trials of diagnostic imaging and image-guided
therapeutic procedures that will result in: 1) the earlier diagnosis of
cancer, 2) allaying the concerns of those who do not have cancer, and 3)
improving the length and quality of lives of cancer patients. Further
information about ACRIN can be found at
www.acrin.org.
The American College of Radiology (ACR) is a
national professional organization serving more than 32,000 diagnostic
radiologists, radiation oncologists, interventional radiologists,
nuclear medicine physicians, and medical physicists, with programs
focusing on the practice of radiology and the delivery of comprehensive
health care services.
NCI leads the National Cancer Program and the NIH
effort to dramatically reduce the burden of cancer and improve the lives
of cancer patients and their families, through research into prevention
and cancer biology, the development of new interventions, and the
training and mentoring of new researchers. For more information about
cancer, please visit the NCI Web site at
http://www.cancer.gov or call NCI's Cancer Information Service at
1-800-4-CANCER (1-800-422-6237).
The National Institutes of Health (NIH) The
Nation's Medical Research Agency includes 27 Institutes and Centers
and is a component of the U.S. Department of Health and Human Services.
It is the primary federal agency for conducting and supporting basic,
clinical and translational medical research, and it investigates the
causes, treatments, and cures for both common and rare diseases. For
more information about NIH and its programs, visit
www.nih.gov.
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Medicare's coverage of tests for colorectal cancer.