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Conrad Notes
a timely medical meeting newsletter
SCREENING FOR COLORECTAL CANCER (CRC)
R.H. Fletcher, MD, MSc, Harvard University School of Medicine and School of Public Health, Boston, Mass, discussed the various options in screening for CRC. Several items are important including test selection, screening risks, patient comfort and convenience, and cost. A recent report on the clinical guidelines and rationale for CRC screening, coauthored by Fletcher, provides details (Gastroenterology 1997;112:594-642).

Cost-effectiveness of screening Direct screening costs vary considerably from the lowest for the fecal occult blood test (FOBT), moderate for double-contrast barium enema (DCBE) and sigmoidoscopy, and highest for colonoscopy. The cost per year of life saved has been estimated as about $20,000 to $30,000. The procedure and accompanying cost usually precedes the benefits by several years.
Selecting the screening test(s) CRC screening tests vary in attendant risk, effectiveness, convenience, patient comfort, cost and available experts. There is strong evidence that FOBT is effectiveve. It is moderately predictive for cancers but low for polyps, presents minimal discomfort and risk to the patient, inexpensive and simple to perform.

Colonoscopy, compared to other tests, has the highest potential for saving lives, is most complex and discomforting to the patient, expensive and risky (complications = 1 to 3/1,000 and deaths about one/tenth as often); in contrast, DCBE-associated deaths are estimated as 1/50,000.

Results of screening Fletcher presented data obtained from a simulation model. Original FOB screening test and subsequent diagnostic surveillance on 100,000 individuals are considered. The model calls for the individuals to have annual FOBTs from age 50 through 85 years or death. This and other input data allow estimating the number of tests conducted, including decennial colonoscopies and if needed for true and false positive FOBT. The model also yielded estimates of the numbers of detected colon cancers, preventable deaths, and procedural deaths.

 FOBTsColonoscopies
Positive Tests 218,312 52,553
Cancers Prevented 2,378 3,570
Deaths Prevented 1,330 1,763
Procedural Deaths 52 73

According to the model, FOBT screening results in fewer scheduled colonoscopies but similar numbers of preventable cancers and procedural deaths. So, Fletcher attributes the costs, risks, and nearly all of the benefit as due to colonoscopy, the final common path. Colonoscopy needs to be simpler, safer, and as inexpensive as possible to increase the benefits of screening.

Who decides? The patient and physician need to jointly consider the various screening tests for CRC. This requires sensitivity to the patient's attitude toward the attendant risk and acceptance of limited information including uncertainty.

Eugene A. Conrad

Presented at the Annual Meeting of the American Society of Clinical Oncology (ASCO) on May 17-20, 1997
CONRAD NOTES, © 1997 All Rights Reserved
Eugene A. Conrad, PhD, MPH / ISSN 1078 / June 1997

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