Dr. Levine is with the Department of Radiology at the
Hospital of the University of Pennsylvania in Philadelphia, PA.
He is also a member of the editorial advisory board of this
journal.
C
olorectal cancer is the second leading cause of cancer deaths in
the United States, with over 130,000 newly diagnosed cases and
50,000 deaths each year. It has been estimated that, without
preventive action, 1 of every 20 Americans will develop this
disease sometime in life. Most colorectal cancers are thought to
develop from preexisting adenomatous polyps that undergo malignant
transformation via a well established adenoma-carcinoma sequence.
Therefore, early detection and removal of colonic adenomas should
substantially decrease morbidity and mortality from colorectal
cancer.
In the past, the American Cancer Society recommended a screening
program for colorectal cancer that included annual fecal occult
blood testing with sigmoidoscopy every 3 to 5 years after the age
of 50. However, more than 50% of colonic neoplasms are located
above the level of the rectosigmoid. Because of the limitations of
sigmoidoscopy in detecting these more proximal lesions, the
American Cancer Society recently endorsed a new set of guidelines
that included a full colon examination--either a double-contrast
barium enema or colonoscopy--at 5- or 10-year intervals in
average-risk persons over the age of 50. The Health Care Finance
Administration (HCFA) also has ruled that double-contrast barium
enemas be included as a reimbursable option in the new national
Medicare coverage for colorectal cancer screening. With this
precedent, other insurers and third-party payers also are likely to
approve the double-contrast barium enema as a reimbursable test for
colorectal cancer screening. As a result, the demand for barium
enema examinations could increase dramatically as we enter the next
millennium.
The new guidelines for colorectal cancer screening have major
implications for practicing radiologists. In the past, barium
enemas typically have been performed as diagnostic studies in
patients with rectal bleeding or other signs or symptoms of
colorectal disease. In contrast, screening barium enemas are
performed in asymptomatic people, as the objective is to find and
remove precursor adenomas and early carcinomas which are highly
curable. Fortunately, the risk of developing colorectal cancer is
related to the development of polyps of 1 cm or greater in size,
and the vast majority of these lesions can be detected on
double-contrast studies. The double-contrast barium enema therefore
is a valuable screening test for colorectal cancer in average-risk
Americans.
Yet there is a catch. If the double-contrast barium enema is to
be an effective screening tool for colorectal cancer, radiologists
must be able to perform and interpret these examinations with the
same skill and expertise needed for other "high-tech" imaging
studies such as CT and MRI. This means that we have to refocus our
priorities in order to acquire or, in some cases, reacquire the
technical and interpretive skills necessary for performing high
quality double-contrast studies. Some radiologists might need to
attend refresher courses, workshops, or even mini-fellowships to
hone their skills. Within a department, a single radiologist might
be assigned overall responsibility for assuring quality control and
establishing technical guidelines for performing these
examinations.
If radiologists are able to offer double-contrast barium enemas
as a safe, inexpensive alternative to colonoscopy for colorectal
cancer screening, the demand for barium enemas could ultimately
surpass our capabilities as providers of this examination. The
recent development and refinement of digital imaging might help to
alleviate this problem by increasing patient throughput with
electronic image acquisition and storage. Another possible solution
is the development of out-patient screening facilities in which
digital barium enema examinations are performed by specially
trained technologists and subsequently interpreted by radiologists.
With the use of teleradiology, radiologists could have geographic
independence, being able to interpret these screening studies at
workstations remote from the sites at which the examinations were
performed. Finally, CT colonography is an exciting new technique
for colorectal cancer screening that has the potential for improved
performance and better patient compliance (see the article in this
issue by C. Daniel Johnson).
Whatever the ultimate solution, we are faced with a new model
for colorectal cancer screening that incorporates the
double-contrast barium enema as a first-line examination for the
detection of colorectal neoplasms. This creates new challenges, and
also new opportunities for radiologists. It is up to us to meet
those challenges.