DECISION MODEL AND COST-EFFECTIVENESS ANALYSIS OF COLORECTAL CANCER
SCREENING AND SURVEILLANCE GUIDELINES FOR AVERAGE-RISK ADULTS
Rezaul K. Khandker, Jane D. Dulski, Jeffrey B. Kilpatrick, Randall P. Ellis, Janet B. Mitchell
Health Economics Research, Inc.
William B. Baine
Agency for Healthcare Research and Quality
Corresponding author: William B. Baine, M..D.
Center for Outcomes and Effectiveness Research
Agency for Healthcare Research and Quality
6010 Executive Boulevard
Rockville, Maryland 20852-3813
Telephone: 301 594-0524
Fax: 301 594-3211
Running head: Cost-effectiveness of colorectal cancer screening
Objectives: Guidelines on colorectal cancer screening and surveillance in people at average risk and at
increased risk have recently been published by the American Gastroenterological Association. The
guidelines for the population at average risk were evaluated using cost-effectiveness analyses. Methods:
Since colorectal cancers primarily arise from precancerous adenomas, a state transition model of disease
progression from adenomatous polyps was developed. Rather than assuming that polyps turn to cancer
after a fixed interval (dwell time), such transitions were modeled to occur as an exponential function of the
age of the polyps. Screening strategies included periodic fecal occult blood test, flexible sigmoidoscopy,
double-contrast barium enema, and colonoscopy. Screening costs were estimated using Medicare and
private claims data, and clinical parameters were based on published studies. Results: Cost per life-year
saved was $12,636 for flexible sigmoidoscopy every five years and $14,394 for annual fecal occult blood
testing. The assumption made for polyp dwell time critically affected the attractiveness of alternative
screening strategies. Conclusions: Sigmoidoscopy every five years and annual fecal blood testing were
the two most cost-effective strategies, but with low compliance, occult blood testing was less cost-
effective. Lowering colonoscopy costs greatly improved the cost-effectiveness of colonoscopy every ten
Keywords: Colonoscopy, Colorectal Neoplasms, Cost-Benefit Analysis, Mass Screening, Occult Blood
The authors gratefully acknowledge the contributions of Francis D. Chesley, M.D., in reviewing this study
and identifying necessary clinical parameters, James P. Summe in developing the database used, William
Yu in commenting on the model and reviewing the manuscript, and Kathleen A. Weis, Dr.P.H., M.S.N.,
R.N., E.N.P.-C, Ph.D., for case definition and review and comment on the model. The study was
conducted under Contract No. 282-95-2002 from the former Agency for Health Care Policy and Research.
An unpublished report (available from the corresponding author upon request) from Health Economics
Research (HER), Inc., to the Agency for Health Care Policy and Research served as the basis for this
paper. The statements contained in this paper are solely those of the authors and do not necessarily
reflect the views or opinions of sponsoring or affiliated organizations. The study was conducted when the
first three authors were employed at HER, Inc.
Colorectal cancer is the second leading cause of cancer death in the United States. Together, colon and
rectal cancers were estimated to account for 131,200 new cancer cases and 54,900 deaths in 1997 (2).
Although a small portion of the population is at high risk of colorectal cancer because of heritable genetic
disorders or as a complication of inflammatory bowel disease, most cases of colorectal cancer develop in
members of the general population without clearly recognized predisposing conditions. These sporadic
cases are now thought to arise through the accumulation of mutations that lead sequentially to the
development of small adenomatous polyps, large adenomas, invasive carcinoma, and, in some persons,
metastatic disease (4).
In 1994, the former Agency for Health Care Policy and Research (AHCPR) contracted with
the American Gastroenterological Association (AGA) to develop guidelines for screening and surveillance
of colorectal cancer. A panel of experts convened by AHCPR and a consortium including AGA, the
American Society for Gastrointestinal Endoscopy, the American College of Colon and Rectal Surgery, the
American College of Gastroenterology, and the Society of American Gastrointestinal Endoscopic
Surgeons developed a set of recommendations that were published under AGA auspices in 1997 (38).
These recommendations present a choice of alternative screening strategies. This study examines these
recommended colorectal cancer screening and surveillance strategies for average-risk adults by using a
decision model and cost-effectiveness framework.
Approximately 30% of persons develop some type of colonic polyp by age 50 (34). Many such
polyps are hyperplastic (generally small and of no clinical importance), but others are adenomatous
(premalignant) and can lead to cancer unless detected and removed early in their growth phase. The
effectiveness of screening average-risk persons is derived from early detection of cancer and removal of
polyps, lowering the incidence of cancer and cancer-related deaths. Early detection of polyps and cancer
can also reduce eventual treatment costs. However, screening everyone for colorectal cancer is
expensive. Whether to screen all persons after a certain age, what types of screening methods to use,
and how frequently to apply the tests are important policy questions. The choice and frequency of tests
determine not only how quickly polyps and cancers are detected and treated but also how much it will cost
to implement such screening and surveillance programs.
This study developed an elaborate model by which polyps may lead to colorectal cancer,
compared alternative screening strategies, and conducted extensive sensitivity analyses. Past studies
have concluded that screening after a certain age can be a cost-effective method of reducing morbidity
and mortality from colorectal cancer (11;12;22;30;34;35). This study significantly extended earlier work in
terms of the assumptions regarding polyp dwell time and post-polypectomy surveillance. While earlier
studies provide comparisons of alternative screening tools, no clear consensus has emerged regarding
the most appropriate screening strategies. In part, this lack of consensus reflects a lack of understanding
of the colorectal cancer disease process, including the dwell times of polyps at different stages of
development. Considerable uncertainly surrounds how polyps progress, and the effectiveness of the
various screening options depends critically on that process. This study particularly addressed this issue
using a disease model that captured the uncertainty associated with polyp dwell time. This model also
built an extensive surveillance period during which screening of heightened intensity could be applied on
the basis of guidelines recommended for the surveillance population.
Screening and Surveillance Strategies
The analyses considered four principal methods of screening for colorectal cancer addressed
by the AGA guidelines (fecal occult blood testing or FOBT, flexible sigmoidoscopy or FSIG, double-
contrast barium enema or DCBE, and colonoscopy) (38). FOBT is widely used to screen for colorectal
cancer because the method is simple and inexpensive. Polyps and cancers may bleed, and FOBT
detects neoplasms by revealing blood in the stool. However, FOBT is least effective at detecting small
polyps. Sigmoidoscopy and colonoscopy permit inspection of the colonic lumen, and barium enemas
display the contours of the colonic mucosa. Sigmoidoscopy does not permit examination beyond the left
(descending) side of the colon, whereas colonoscopy offers the potential of surveying the entire colon.
Colonoscopy can be used both as a screening and as a surveillance procedure and is often selected to
follow other screening tests when polyps or cancer are suspected. Removal of polyps (polypectomy) can