Computed tomographic colonoscopy can detect cancer outside of colon
28 July 2005
Oak Brook, Ill., USA. The investigation of the colon using computed
tomography can detect cancers and other important conditions outside of the
colon. Conventional colonoscopy only examines the inside of the colon and
would therefore miss these.
Computed tomographic colonoscopy (CTC), also known as virtual
colonoscopy, is a non-invasive screening method for colon cancer. Virtual
colonoscopy uses a series of CT images to visually reconstruct the interior
of the colon on a computer. Unlike standard colonoscopy, which
explores only the interior of the colon, virtual colonoscopy depicts the
surrounding areas as well.
The study, reported in the August 2005 issue of Radiology, was headed by
Dr Judy Yee, Chief of Radiology at the Veterans Affairs Medical Center and
Associate Professor and Vice Chair of Radiology at University of California
San Francisco School of Medicine.
"The chance of finding cancer outside the colon may be as significant as
the chance of finding cancer inside the colon," said Judy Yee, M.D., Chief
of Radiology at the Veterans Affairs Medical Center and associate professor
and Vice Chair of radiology at University of California San Francisco School
of Medicine. "Using the same amount of radiation as a non-contrast CT scan
of the abdomen/pelvis, you can do a virtual colonoscopy and screen the
surrounding abdominal and pelvic area."
To evaluate the prevalence of extracolonic findings at virtual
colonoscopy and to determine the cost of follow-up testing, Dr. Yee and
colleagues performed CTC on 500 men, including 194 (39 percent) considered
average risk and 306 (61 percent) at high risk for colon cancer. The mean
age of the men was 62.5. Of the 500 patients in the study, 315 (63 percent)
had extracolonic findings. Forty-five (9 percent) patients had clinically
important extracolonic findings.
Findings deemed clinically important included large aneurysms, suspicious
lesions and masses in the solid organs of the abdomen, lymphadenopathy,
pulmonary nodules and gallbladder wall thickening. The mean additional cost
per CTC exam to work up the important findings was $28.12.
"The fact that the additional cost was so low indicates that this
procedure is potentially cost effective, not only in regards to the
colonoscopy but for other conditions as well," Dr. Yee said.
Dr. Yee's research represents the longest follow-up (3.6 years) of
patients after CTC and is one of the first to include average-risk patients
among the study cohort. There was no significant difference between the
numbers of clinically important findings in average-risk and high-risk
Radiological Society of North America:
University of California San Francisco School of Medicine: