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.