||Screening For Colorectal Cancer
Information For Health Professionals From The US Preventive Services Task Force
Screening for colorectal cancer is recommended for
all persons aged 50 and older with annual fecal occult blood testing (FOBT),
or sigmoidoscopy (periodicity unspecified), or both (see Clinical Intervention
). There is insufficient
evidence to determine which of these screening methods is preferable or whether
the combination of FOBT and sigmoidoscopy produces greater benefits than does
either test alone. There is also insufficient evidence to recommend for or
against routine screening with digital rectal examination, barium enema, or
colonoscopy, although recommendations against such screening in average-risk
persons may be made on other grounds (see Clinical Intervention
). Persons with
a family history of hereditary syndromes associated with a high risk of colon
cancer should be referred for diagnosis and management (see Clinical Intervention
Burden of Suffering
cancer is the second most common form of cancer in the U.S. and has the second
highest mortality rate, accounting for about 140,000 new cases and about 55,000
deaths each year.
An individual's lifetime risk
of dying of colorectal cancer in the U.S. has been estimated to be 2.6%.
About 60% of patients with colorectal cancer have regional
or distant metastases at the time of diagnosis.
Estimated 5-year survival is 91% in persons with localized disease, 60% in
persons with regional spread, and only 6% in those with distant metastases.
The average patient dying of colorectal cancer loses 13
years of life.
In addition to the mortality associated
with colorectal cancer, this disease and its treatment -- surgical resection,
colostomies, chemotherapy, and radiotherapy -- can produce significant
morbidity. Persons at highest risk of colorectal cancer include those with
uncommon familial syndromes (i.e., hereditary polyposis and hereditary nonpolyposis
colorectal cancer [HNPCC]) and persons with longstanding ulcerative colitis.
Familial syndromes are estimated
to account for 6% of all colorectal cancers,
various genetic mutations associated with these syndromes have been identified.[4A]
Other principal risk factors include a history of colorectal
cancer or adenomas in a first-degree relative, a personal history of large
adenomatous polyps or colorectal cancer, and a prior diagnosis of endometrial,
ovarian, or breast cancer. In an analysis of two large cohorts involving
over 840,000 patient-years of follow-up, a family history of colorectal cancer
was associated with a significant increase in risk in younger persons (1.7-4-fold
increase between ages 40 and 60), but was not associated with a significantly
increased risk in persons after age 60;[4B]
higher in persons with more than one affected relative. The absolute increase
in lifetime risk in persons with a family history was modest, however: an
estimated cumulative incidence of colorectal cancer by age 65 of 4% vs. 3%
in persons without a family history.[4B]
in fat or low in fiber may also increase the risk of colorectal cancer.
The principal screening tests for detecting colorectal
cancer in asymp-tomatic persons are the digital rectal examination, FOBT,
and sigmoidoscopy. Less frequently mentioned screening tests include barium
enema and colonoscopy, which have been advocated primarily for high-risk groups.
The digital rectal examination is of limited value as a screening test for
colorectal cancer. The examining finger, which is only 7-8 cm long,
has limited access even to the rectal mucosa, which is 11 cm in length. A
negative digital rectal examination provides little reassurance that the patient
is free of colorectal cancer because fewer than 10% of colorectal cancers
can be palpated by the examining finger.
A second screening maneuver is FOBT. The reported sensitivity and specificity
of FOBT for detecting colorectal cancer in asymptomatic persons are 26-92%
and 90-99%, respectively (usually based on two samples from three different
stool specimens), with the widely varying estimates reflecting differences
in study designs.
Positive reactions on guaiac impregnated cards, the most
common form of testing, can signal the presence of bleeding from premalignant
adenomas and early-stage colorectal cancers. The guaiac test can also produce
false-positive results, however. The ingestion of foods containing peroxidases,
and gastric irritants such as salicylates and other antiinflammatory
can produce false-positive test results for
neoplasia. Nonneoplastic conditions, such as hemorrhoids, diverticulosis,
and peptic ulcers, can also cause gastrointestinal bleeding. FOBT can also
miss small adenomas and colorectal malignancies that bleed intermittently
or not at all.
of false-negative results include heterogeneous distribution of blood in feces,
ascorbic acid and other antioxidants that interfere with
and extended delay before testing
As a result, when FOBT
is performed on asymptomatic persons, the majority of positive reactions are
falsely positive for neoplasia. The reported positive predictive value among
asymptomatic persons over age 50 is only about 2-11% for carcinoma and
20-30% for adenomas.
Assuming a false-positive rate of 1-4%, a person
who receives annual FOBT from age 50 to age 75 has an estimated 45% probability
of receiving a false-positive result.
proportion of false-positive results is an important concern because of the
discomfort, cost, and occasional complications associated with follow-up diagnostic
tests, such as barium enema and colonoscopy.
Rehydration of stored slides can improve sensitivity, but
this occurs at the expense of specificity.
study, rehydration improved sensitivity from 81% to 92%, but it decreased
specificity from 98% to 90% and lowered positive predictive value from 6%
to 2%. Due to the high false-positive rate, about one third of the entire
screened population of asymptomatic patients underwent colonoscopy for abnormal
FOBT results within a 13-year period.
Other tests have been proposed to improve the accuracy of screening
occult blood. Current evidence is equivocal as to whether HemoQuant (SmithKline
Diagnostics, Sunnyvale, CA), a quantitative measurement of hemoglobin in the
stool, has better sensitivity or specificity than does qualitative FOBT.
Recently developed hemoglobin immunoassays offer the promise
of improved sensitivity and specificity but require further evaluation before
being considered for routine screening.
The third screening test for colorectal cancer is sigmoidoscopy. Sigmoidoscopic
screening in asymptomatic persons detects 1-4 cancers per 1,000 examinations.
However, the sensitivity and diagnostic
yield of sigmoidoscopy screening varies with the type of instrument: the rigid
(25 cm) sigmoidoscope, the short (35 cm) flexible fiberoptic sigmoidoscope,
or the long (60 cm) flexible fiberoptic sigmoidoscope. Since only 30% of
colorectal cancers occur in the distal 20 cm of bowel, and less than half
occur in or distal to the sigmoid colon,
length of the sigmoidoscope has a direct effect on case detection. The rigid
sigmoidoscope, which has an average depth of insertion of about 20 cm
and allows examination to just above the rectosigmoid junction,
can detect only about 25-30% of colorectal cancers.
The 35-cm flexible sigmoidoscope, however, can visualize about 50-75%
of the sigmoid colon and can detect about 50-55% of polyps. Longer
60-cm instruments have an average depth of insertion of 40-50 cm, reaching
the proximal end of the sigmoid colon in 80% of examinations
with the capability of detecting 65-75% of polyps
and 40-65% of colorectal cancers
have examined the feasibility of introducing a 105-cm flexible sigmoidoscope
in the family practice setting,
but it is unclear
whether the added length substantially increases the rate of detection of
premalignant or malignant lesions. Barium enema studies have confirmed that
some neoplasms within reach of the sigmoidoscope may not be seen on endoscopy.
Sigmoidoscopy can also produce false-positive
results, primarily by detecting polyps that are unlikely to become malignant
during the patient's lifetime. Autopsy studies have shown that 10-33%
of older adults have colonic polyps at death,
only 2-3% have colorectal cancer.
Depending on the type of adenomatous polyp, an estimated
5-40% eventually become malignant,
that takes an average of 10-15 years.
It follows that the majority of asymptomatic persons with
colonic polyps discovered on routine sigmoidoscopic examination will not develop
clinically significant malignancy during their lifetime. For these persons,
interventions that typically follow such a discovery (i.e., biopsy, polypectomy,
frequent colonoscopy), procedures that are costly, anxiety provoking, and
potentially harmful, are unlikely to be of significant clinical benefit.
Other potential screening tests for colorectal cancer include colonoscopy
and barium enema, which appear to have comparable accuracy. About 95% of
colorectal cancers are within reach of the colonoscope, and the examination
has an estimated 75-95% sensitivity in detecting lesions within its
requires sedation and often involves the use of a hospital suite, is more
expensive than other screening tests and has a higher risk of anesthetic and
procedural complications. The estimated sensitivity and specificity of air-contrast
barium enema in detecting lesions within its reach are about 80-95%
and 90%, respectively, using subsequent diagnosis as a reference standard.
Some retrospective studies have reported a higher sensitivity
of barium enema for detecting colorectal cancer (about 90-96%),
with pathologic diagnosis as the
reference standard, but these estimates generally do not account for the selection
bias introduced by the case-selection methods.
Effectiveness of Early Detection
Persons with early-stage
colorectal cancer at the time of diagnosis appear to have longer survival
than do persons with advanced disease.
is little information on the extent to which lead-time and length biases (see Chapter ii) account for these differences, researchers
in the U.S. and Europe launched large clinical trials in the late 1970s to
collect prospective data on the effects of screening on co-lorectal cancer
Two of these trials
examined the effect of routine FOBT on colorectal cancer
mortality. A randomized controlled trial involving over 46,000 volunteers
over age 50 found that the 13-year cumulative mortality from colorectal cancer
was 33% lower among persons advised to undergo annual FOBT (5.9 deaths per
1,000) than among a control group that was not offered screening (8.8 deaths
The report provided insufficient data,
however, to determine to what extent observed differences in outcome were
attributable to FOBT or to the large number of colonoscopies that were performed
due to frequent false-positive FOBT. An analysis of the study data by other
authors suggested that one third to one half of the mortality reduction was
due to "chance" selection of persons for colonoscopy,
but the assumptions in the analysis have been disputed by the authors.
Another controlled trial,
was not randomized, assigned over 21,000 patients to a control group that
received a standard periodic health examination or to a study group that was
also offered FOBT; both groups received sigmoidoscopy screening. Among new
patients (first visit to the preventive medicine clinic), colorectal cancer
mortality was 43% lower in the study group than in controls, a difference
of borderline statistical significance (p = 0.053, one-tail), and there was
no difference in outcomes among patients seen previously at the clinic. Recent
case-control studies have also reported a 31-57% reduction in risk among
persons receiving FOBT.
Three large clinical trials of FOBT screening, currently under way in Europe,
are expected to report their results in the coming years.
studies have provided important information on the effectiveness of sigmoidoscopy
screening. The largest study found that 9% of persons who died of colorectal
cancer occurring within 20 cm of the anus had previously undergone a rigid
sigmoidoscopic examination, whereas 24% of persons in the control group had
received the test.
The adjusted odds ratio of 0.41
(95% confidence interval, 0.25-0.69) suggested that sigmoidoscopy screening
reduced the risk of death by 59% for cancers within reach of the sigmoidoscope.
The investigators noted that the adjusted odds ratio for patients who died
of more proximal colon cancers was 0.96. This finding added support to the
hypothesis that the reduced risk of death from cancers within reach of the
rigid sigmoidoscope was due to screening rather than to confounding factors.
Another case-control study reported that the odds ratio for dying of colorectal
cancer was 0.21 in screened subjects, and the benefit appeared to be limited
to cancers within the reach of the sigmoidoscope.
Older evidence of the effectiveness of sigmoidoscopy screening suffered
from important design limitations. A randomized controlled trial of multiphasic
health examinations, which included rigid sigmoidoscopy, reported that the
study group had significantly lower incidence and mortality rates from colorectal
A subsequent analysis of the data, however, revealed that the proportion
of subjects receiving sigmoidoscopy and the rate of detection or removal of
polyps were similar in both the study and control groups, thus suggesting
little benefit from sigmoidoscopy.
Two large screening
programs found that persons receiving periodic rigid sigmoidoscopy had less
advanced disease and better survival from colon cancer than was typical of
the general population.
However, both studies lacked internal controls and used
nonrandomized methods to select participants; other methodologic problems
with these investigations are outlined in other reviews.
An important consideration in assessing the
effectiveness of sigmoidoscopic screening is the potential iatrogenic risk
associated with the procedure. Complications from sigmoidoscopy are relatively
rare in asymptomatic persons but can be potentially serious. Perforations
are reported to occur in approximately 1 of 1,000-10,000 rigid sigmoidoscopic
Although there are fewer data available on flexible sigmoidoscopy,
the complication rate appears to be less than or equal to that observed for
rigid sigmoidoscopy. The reported risk of perforation from colonoscopy is
about one in 500-3,000 examinations,
and the risk of serious bleeding is 1 in 1,000.
The estimated risk of perforation during barium enema is 1 in 5,000-10,000
There is little useful
evidence regarding the effectiveness of colonoscopy or barium enema screening
in asymptomatic persons. Several recent studies describe colonoscopy screening
of asymptomatic persons, but they report only the anatomic distribution of
polyps and do not address clinical outcomes.
A prospective study demonstrated
a significantly lower incidence of subsequent colorectal cancer in patients
with previously diagnosed adenomas who received periodic colonoscopy and polypectomy,
but potential biases in the control groups (historical controls and population
incidence rates) prevent definitive conclusions.
No studies have directly examined the effectiveness of routine barium enema
screening in decreasing colorectal cancer mortality in asymptomatic persons.
Modeling studies suggest its effectiveness might be comparable to a screening
strategy of periodic sigmoidoscopy.
There is limited information on the optimal age to begin or end screening
and the frequency with which it should be performed. The age groups in which
screening has been shown to decrease mortality are ages 50-80 for FOBT
and over age 45 for sigmoidoscopy.
Theoretically, the potential yield from screening should increase beyond
age 50 since the incidence of colorectal cancer after this age doubles every
Modeling studies suggest that beginning
screening at age 40 rather than at age 50 offers no improvement in life expectancy.
There is little evidence from which to determine the proper
age for discontinuing screening. The optimal interval for screening is less
certain for sigmoidoscopy than for FOBT, for which there is good evidence
of benefit from annual screening. A modeling study of sigmoidoscopy screening
estimated that an interval of 10 years would preserve 90% of the effectiveness
of annual screening; this model assumes that adenomatous polyps take 10-14
years to become invasive cancers.
Another model suggested
that an interval of 2-4 years would allow detection of 95% of all polyps
greater than 13 mm in diameter.
In a case-control
study, the risk reduction associated with sigmoidoscopy screening did not
diminish during the first 9-10 years after sigmoidoscopy.
Other studies suggest that a single sigmoidoscopic screening examination
may be adequate for low-risk individuals,
being investigated in the United Kingdom.
Primary preventive measures to prevent colorectal cancer are currently
under investigation. An association between colorectal cancer and dietary
intake of fat and fiber has been demonstrated in a series of epidemiologic
studies (see Chapter 56). Case-control
and cohort studies also suggest that aspirin use may decrease the risk of
Recommendations of Other Groups
The American Cancer Society recommends annual digital rectal examination
for all adults beginning at age 40, annual FOBT beginning at age 50, and sigmoidoscopy
every 3-5 years beginning at age 50.
recommendations have been issued by the American Gastroenterological Association,
the American Society for Gastrointestinal Endoscopy,
and the American College of Obstetricians and Gynecologists.
The American College of Physicians' (ACP) guidelines, revised
in 1995, recommend offering a variety of screening options to persons from
age 50 to 70, depending on local resources and patient preferences: flexible
sigmoidoscopy, colonoscopy, or air-contrast barium enema, repeated at 10-year
intervals. The ACP recommends that annual FOBT be offered to persons who
decline these screening tests, but concluded that there was relatively little
benefit of continuing endoscopic screening beyond age 70 in individuals who
had been adequately screened up to that age.
American College of Radiology recommends screening with barium enema every
3-5 years as an equivalent alternative to periodic sigmoidoscopy.
The recommendations of the American Academy of Family Physicians
are currently under review.
Most organizations recommend
more intensive screening of those in high-risk groups (e.g., familial polyposis,
inflammatory bowel disease) with periodic colonoscopy or barium enema. The
Canadian Task Force on the Periodic Health Examination concluded that there
was insufficient evidence to support screening of asymptomatic individuals
over age 40 but that persons with a history of cancer family syndrome should
be screened with colonoscopy.
An expert panel convened
by the Agency for Health Care Policy and Research is expected to issue guidelines
for colorectal cancer screening and surveillance in 1996.
In summary, recent studies
have provided compelling evidence of the effectiveness of FOBT and sigmoidoscopy
screening, but the evidence is not definitive. At least one randomized controlled
trial and several observational studies have shown that annual FOBT in persons
over age 50 can reduce colorectal cancer mortality. This evidence does not,
however, clarify whether the observed benefits were due to FOBT or to the
effect of performing colonoscopy on a large proportion of the screened population.
For sigmoidoscopy, a case-control study supports a strong association between
regular screening and reduced colorectal cancer mortality from cancers within
reach of the sigmoidoscope. This study was limited, however, by its small
number of cases, potential selection biases, and inability to provide prospective
evidence of benefit. There are additional concerns about the adverse effects,
costs, and optimal frequency of screening. Studies that will help resolve
these uncertainties are currently in progress; the final results of ongoing
European FOBT trials will be unavailable for several years, however, and a
large United States study
of FOBT and sigmoidoscopy
screening will not be completed until the turn of the century.
An important limitation to the effectiveness of screening for colorectal
is the ability of patients and clinicians to comply with testing. Patients
may not comply with FOBT for a variety of reasons,
but compliance rates are generally higher than for sigmoidoscopy.
Recent clinical trials report compliance rates of 50-80% for FOBT among
but lower rates (about 15-30%)
have been reported in community screening programs.
Although the introduction of
flexible fiberoptic instruments has made sigmoidoscopy more acceptable to
the procedure remains uncomfortable, embarrassing,
and expensive, and therefore many patients may be reluctant to agree to this
test. A survey of patients over age 50 found that only 13% wanted to receive
a sigmoidoscopy examination after being advised that they should receive the
test; the most common reasons cited for declining the test were cost (31%),
discomfort (12%), and fear (9%).
In a study in
which sigmoid-oscopy was recommended repeatedly, only 31% of participants
consented to the procedure,
but this study was performed during years when rigid sigmoidoscopy
was common. Compliance rates as low as 6-12% have been reported. Studies
suggest that physician motivation is a major determinant of patient compliance,
and physicians may be reluctant
to perform screening sigmoidoscopy on asymptomatic persons. It has been estimated
that a typical family physician with 3,000 active patients (one third aged
50 or older) would have to perform five sigmoidoscopies daily to initially
screen the population and two daily procedures for subsequent screening.
In addition, examinations using 60-cm sigmoidoscopes are
require more extensive training
than do those using shorter instruments.
limitation to screening is its cost. Although a formal cost-effectiveness
analysis of screening for colorectal cancer is beyond the scope of this chapter,
the economic implications associated with the widespread performance of FOBT
and sigmoidoscopy are clearly significant. A single flexible sigmoidoscopic
examination costs between $100 and $200.
A policy of routine FOBT and sigmoidoscopic screening
of all persons in the United States over age 50 (about 63 million persons)
would cost over $1 billion per year in direct charges.
Others have calculated that FOBT screening alone could cost the United States
and Canada between $500 million and $1.2 billion each year.
Another model predicted that performing annual FOBT on
persons over age 65 would cost about $35,000 per year of life saved; adding
flexible sigmoidoscopy would increase the cost to about $42,000 to $45,000
per year of life saved.
Mathematical models suggest
that barium enema screening every 3-5 years might have comparable or
superior cost-effectiveness when compared with sigmoidoscopy screening, but
neither the clinical effectiveness nor acceptability of barium enema screening
has been demonstrated directly in clinical studies.
effects of screening are also of concern. The logistical difficulties and
costs of performing FOBT and sigmoidoscopy on a large proportion of the U.S.
population are significant, due to the limited acceptability of the tests
and the expense of performing screening and follow-up on a large proportion
of the population. Moreover, the tests have potential adverse effects that
must be considered, such as false-positive results that lead to expensive
and potentially harmful diagnostic procedures. Studies that have reported
reduced mortality from FOBT used rehydrated slides to increase sensitivity,
thereby producing a higher proportion of false-positive results than with
nonrehydrated slides; 32% of the annually screened population underwent colonoscopy
during a 13-year follow-up period.
If this rate is
extrapolated to the 63 million Americans over age 50 who would receive annual
FOBT, it can be predicted that about 20 million persons would require colonoscopy.
The full implications of this "screening cascade" need to be
considered, along with the scientific evidence of clinical benefits, before
reaching conclusions about appropriate public policy. For example, using
nonrehydrated slides rather than rehydrated slides could substantially reduce
the adverse effects and costs of a national screening program. As noted earlier,
data from a major screening trial suggest that using nonrehydrated slides
rather than rehydrated slides could increase the positive predictive value
of FOBT from 2% to 6%, subjecting far fewer screened persons to unnecessary
colonoscopy. This improvement in specificity, however, comes at the expense
of sensitivity, which decreased from 92% with rehydration to 81% in nonrehydrated
slides. The use of nonrehydrated slides would therefore allow a much larger
proportion of persons with cancer to escape detection.
considerations that apply to persons at increased risk of colorectal cancer
are complicated by inadequate epidemiologic and effectiveness data and inconsistent
disease classifications. Having a single family member with colorectal cancer
does not carry the high risk associated with hereditary cancer syndromes (e.g.,
familial polyposis, HNPCC).
A family history that is suggestive of the latter includes a pattern of diagnoses
consistent with autosomal dominant inheritance of a highly penetrant disorder.
Characteristic features include a family history of colorectal cancer being
diagnosed at an early age, frequent cases of multiple primary cancers, or
florid adenomatous colonic polyps. Performing periodic colonoscopy to screen
for cancer in these groups may be justified in light of the high risk of disease
and the incidence of proximal colonic lesions, but there is no direct evidence
to determine the optimal strategy in this population.
Screening for colorectal cancer is recommended for
all persons aged 50 or over ("B" recommendation). Effective methods include
FOBT and sigmoidoscopy. There is insufficient evidence to determine which
of these screening methods is preferable or whether the combination of FOBT
and sigmoidoscopy produces greater benefits than either test alone. Although
there is good evidence to support FOBT on an annual basis, there is insufficient
evidence to recommend a periodicity for sigmoidoscopy screening. A frequency
of every 3-5 years has been recommended by other groups on the basis
of expert opinion, and a well-designed case-control study suggests that protection
remains unchanged for at least 10 years after rigid sigmoid-oscopy. Current
evidence suggests that at least some of the benefits of FOBT in reducing colorectal
cancer mortality may be achieved through colonoscopic evaluation of abnormal
results. Widespread FOBT or sigmoidoscopy screening is therefore likely to
generate substantial direct and indirect costs. Appropriate public policy
may require consideration of factors other than the scientific evidence of
clinical benefit. The appropriate age to discontinue screening has not been
Patients who are offered
these tests should receive information about the potential benefits and harms
of the procedures, the probability of false-positive results, and the nature
of the tests that will be performed if an abnormality is detected. FOBT screening
should adhere to current guidelines for dietary restrictions, sample collection,
and storage. Although slide rehydration increases the sensitivity of FOBT,
it also decreases specificity, and there is insufficient evidence to determine
whether rehydration results in better outcomes than screening with nonrehydrated
slides. Sigmoidoscopy should be performed by a trained examiner. The instrument
should be selected on the basis of examiner expertise and patient comfort.
Longer (e.g., 60-cm instrument) flexible sigmoidoscopes have greater sensitivity
and are more comfortable than shorter, rigid sigmoidoscopes.
There is insufficient evidence to recommend for
or against routine screening with digital rectal examination, barium enema,
or colonoscopy ("C" recommendation). Recommendations against using these
tests for screening average-risk persons may be made on other grounds (e.g.,
availability of alternate tests of proven effectiveness, inaccuracy of digital
rectal examination, costs and risks of colonoscopy).
In persons with a single first-degree relative with
it is not clear that the modest increase in the absolute risk of cancer justifies
routine use of colonoscopy over other screening methods. The increased risk
of developing cancer at younger ages may justify beginning screening before
age 50 in persons with a positive family history, however, especially when
affected relatives developed colorectal cancer at younger ages. Direct evidence
of the benefit of screening in younger persons is not available for any group.
For persons with a family history of hereditary syndromes associated with
a very high risk of colon cancer (i.e., familial polyposis or HNPCC), as well
as those previously diagnosed with ulcerative colitis, high-risk adenomatous
polyps, or colon cancer, regular endoscopic screening is part of routine diagnosis
and management; referral to specialists is appropriate for these high-risk
The draft update of this chapter was prepared
for the U.S. Preventive Services Task Force by Steven H. Woolf, MD, MPH.
Tong T, Bolden S.
Cancer statistics, 1995. CA Cancer
J Clin 1995;45:8-30.
Ries LAG, Miller BA, Hankey BF, et al, eds.
SEER cancer statistics review,
1973-1991: tables and graphs. Bethesda: National
Cancer Institute, 1994. (NIH Publication no. 94-2789.)
Winawer SJ, Shike M.
Prevention and control
of colorectal cancer. In: Greenwald P, Kramer BS, Weed DL, eds. Cancer prevention
and control. New York: Marcel Dekker, 1995:537-559.
Hereditary gastrointestinal polyposis
and nonpolyposis syndromes. N Engl J Med 1994;331:1694-1702.
Toribara NW, Sleisenger MH.
for colorectal cancer. N Engl J Med 1995;332:861-867.
Fuchs CS, Giovannucci EL, Colditz
GA, et al.
A prospective study of family history and the risk of colorectal
cancer. N Engl J Med 1994;331:1669-1674.
Mandel JS, Bond JH, Church TR,
Reducing mortality from colorectal cancer by screening for fecal
occult blood. N Engl J Med 1993;328:1365-1371.
Winawer SJ, Flehinger BJ, Schottenfeld
D, Miller DG.
Screening for colorectal cancer with fecal occult blood
testing and sigmoidoscopy. J Natl Cancer Inst
J, Asztely M, Engaras B, Haglind E, Svanvik J, Ahren C.
A randomised trial
of faecal occult blood testing for early detection of colorectal cancer: results
of screening and rescreening of 51,325 subjects. In: Miller AB, Chamberlain
J, Day NE, Hakama M, Prorok PC, eds. Cancer screening. Cambridge, England:Cambridge
University Press, 1991:117-125.
Thomas WM, Pye G, Hardcastle JD, Walker AR.
Screening for colorectal carcinoma:
an analysis of the sensitivity of Haemoccult. Br J Surg 1992;79:833-835.
Ahlquist DA, Wieland HS, Moertel CG, et al.
Accuracy of fecal occult blood
screening for colorectal neoplasia: a prospective study using Hemoccult and
HemoQuant tests. JAMA 1993;269:1262-1267.
St John DJB, Young GP, McHutchison
JG, Deacon MC, Alexeyeff MA.
Comparison of the specificity and sensitivity
of Hemoccult and HemoQuant in screening for colorectal neoplasia. Ann Intern Med 1992;117:376-382.
Influence of diet on occult blood
tests. Gut 1965;6:595-598.
Rees WD, Turnberg LA.
the effects of aspirin on the stomach. Lancet
Freeman LD, Mottet MD, et al.
Sensitivity of guaiac-impregnated cards
for the detection of colorectal neoplasia. J Clin Gastroenterol 1983;5:127-130.
Griffith CDM, Turner DJ, Saunders JH.
False-negative results of Hemoccult
test in colorectal cancer. BMJ 1981;283:472.
Rosenfield RE, Kochwa S, Kaczera
Z, et al.
Nonuniform distribution of occult blood in feces. Am J Clin Pathol 1979;71:204-209.
Jaffe RM, Kasten B, Young DS, et al.
stool occult blood tests caused by ingestion of ascorbic acid (vitamin C).
Ann Intern Med 1975;83:824-826.
Morris DW, Hansell JR, Ostrow D, et al.
of chemical tests for fecal occult blood in hospitalized patients. Dig Dis 1976;21:845-852.
Windeler J, Kobberling J.
Colorectal cancer and Haemoccult.
A study of its value in mass screening using meta-analysis. Int J Colon Dis 1987;2:223-228.
Bang KM, Tillett S, Hoar SK, et al.
Sensitivity of fecal
Hemoccult testing and flexible sigmoidoscopy for colorectal cancer screening.
J Occup Med 1986;28:709-713.
Winawer SJ, Schottenfeld D, Flehinger BJ.
cancer screening. J Natl Cancer Inst 1991;83:243-253.
Eddy DM, Ferioli C, Anderson DS.
for colorectal cancer. Ann Intern Med 1996
Brandeau ML, Eddy DM.
workup of the asymptomatic patient with a positive fecal occult blood test.
Med Decis Making 1987;7:32-46.
Colon cancer screening:
the dilemma of positive screening tests. Arch Intern
Wells HJ, Pagano JF.
"Hemoccult" (TM) test-reversal of false-negative
results due to storage. Gastroenterology 1977;72:1148.
Schwartz S, Dahl J, Ellefson M,
The HemoQuant test: a specific and quantitative determination of
heme (hemoglobin) in feces and other materials. Clin
Ahlquist DA, McGill DB, Schwartz S, et al.
HemoQuant, a new quantitative
assay for fecal hemoglobin: comparison with Hemoccult. Ann Intern Med 1984;101:297-302.
Ahlquist DA, McGill DB, Schwartz S, et al.
Fecal blood levels
in health and disease: a study using HemoQuant. N Engl
J Med 1985;312:1422-1428.
Ahlquist DA, McGill DB, Fleming JL, et al.
Patterns of occult bleeding
in asymptomatic colorectal cancers. Cancer
AM, Crowson TW, Rich EC.
Cost-effectiveness of HemoQuant versus Hemoccult
for colorectal cancer screening. J Gen Intern Med
DJB, Young GS, Alexeyeff M, et al. Most large and medium colorectal adenomas
can be detected by immunochemical occult blood tests. Gastroenterology 1990;98(suppl):A312.
Songster CL, Barrows GH, Jarrett DP.
of fecal occult blood -- the fecal smear punch-disc test: a noninvasive
screening test for colorectal cancer. Cancer
in detection and diagnosis in the asymptomatic individual. Cancer 1971;28:121-122.
Screening flexible sigmoidoscopy: is it worthwhile? An opposing
view. J Fam Pract 1987;25:604-607.
Cady N, Persson AV, Monson DO, et al.
patterns of colorectal carcinoma. Cancer 1974;33:422-426.
Rhodes JB, Holmes FF, Clark GM.
distribution of primary cancers in the large bowel. JAMA 1977;238:1641-1643.
Abrams JS, Reines HD.
Increasing incidence of right-sided lesions in colorectal
cancer. Am J Surg 1979;137:522-526.
colorectal neoplasms. A left-to-right shift of polyps and cancer. Am J Surg 1983;49:62-65.
Winnan G, Berci G, Panish J, et al.
Superiority of the flexible
to the rigid sigmoidoscope in routine proctosigmoidoscopy. N Engl J Med 1980;302:1011-1012.
Bohlman TW, Katon RM, Lipshutz GR, et al.
an evaluation and comparison with rigid sigmoidoscopy. Gastroenterology 1977;72:644-649.
Winawer SJ, Leidner SD, Boyle C, et al.
Comparison of flexible
sigmoidoscopy with other diagnostic techniques in the diagnosis of rectocolon
neoplasia. Dig Dis Sci 1979;24:277-281.
Marks G, Boggs HW, Castro AF,
Sigmoidoscopic examinations with rigid and flexible fiberoptic
sigmoidoscopes in the surgeon's office. Dis Colon Rectum 1979;22:162-169.
Protell RL, Buenger N, Gilbert DA, et al.
The short colonoscope: preliminary
analysis of a comparison with rigid sigmoidoscopy and Hemoccult testing. Gastrointest Endosc 1978;24:208.
Nivatvongs S, Fryd DS.
How far does the proctosigmoidoscope
reach? N Engl J Med 1980;303:380-382.
Nicholls RJ, Dube S.
of examination by rigid sigmoidoscopy. Br J Surg
Shatz BA, Freitas
Area of colon visualized through the sigmoidoscope. JAMA 1954;156:717-719.
Gillespie PE, Chambers TJ, Chan KW, et al.
Colonic adenomas: a colonoscopic
survey. Gut 1979;20:240-245.
Lehman GA, Buchner DM, Lappas JC.
extent of fiberoptic sigmoidoscopy. Gastroenterology 1983;84:803-808.
Lieberman DA, Smith FW.
Screening for colon malignancy with colonoscopy. Am J Gastroenterol 1991;86:946-951.
Johnson DA, Gurney MS, Volpe RJ, Jones DM,
A prospective study of the prevalence of colonic neoplasms in asymptomatic
patients with an age-related risk. Am J Gastroenterol 1990;85:969-974.
Tedesco FJ, Waye JD, Avella JR, Villalobos MM.
of the spatial distribution of colonic mass lesions (polyps and cancers):
a prospective colonoscopic study. Gastrointest Endosc 1980;26:95-97.
Shinya H, Wolff WI.
Morphology, anatomic distribution and cancer potential
of colonic polyps: an analysis of 7,000 polyps endoscopically removed. Ann Surg 1979;190:679-683.
Winawer SJ, Gottlieb LS, Stewart ET, et al.
report of the National Polyp Study. Gastroenterology 1983;84:1352.
Feasibility of 105-cm flexible sigmoidoscopy in family practice. J Fam Pract 1986;23:341-344.
Glick SN, Teplick SK, Balfe DM, et al.
colonoscopic neoplasms missed by endoscopy. Am J Radiol 1989;152:513-517.
Correa P, Strong JP, Reif A, et al.
The epidemiology of colorectal polyps:
prevalence in New Orleans and international comparisons. Cancer 1977;39:2258-2264.
The incidence of benign and malignant neoplasms of the colon
and rectum: a postmortem study. NZ J Surg
Auerback O, Garfinke L, et al.
Adenomatous lesions of the large bowel:
an autopsy survey. Cancer 1979;43:1847-1857.
Williams AR, Balasooriy BAW, Day
Polyps and cancer of the large bowel: a necropsy study in Liverpool.
Muto T, Bussey HJR, Morson BC.
of cancer of the colon and rectum. Cancer
Evolution of cancer of the colon and rectum. Cancer 1974;34:845-849.
The evolution of colorectal carcinoma. Clin Radiol 1984;35:425-431.
Johnson CD, Carlson HC, Taylor WF, Weiland LP.
of carcinoma of the colon: sensitivity of double- and single-contrast studies. Am J Radiol 1983;140:1143-1149.
Radiographic findings in overlooked
colon carcinoma: a retrospective analysis. Acta Radiol 1988;29:331-336.
Lang CA, Ransohoff DF.
Fecal occult blood screening for colorectal cancer:
is mortality reduced by chance selection for screening colonoscopy? JAMA 1994;271:1011-1013.
Mandel JS, Ederer F, Church T, Bond J.
Screening for colorectal
cancer: which test is best? [letter]. JAMA
Selby JV, Friedman
GD, Quesenberry CP, Weiss NS.
Effect of fecal occult blood testing on
mortality from colorectal cancer: a case-control study. Ann Intern Med 1993;118:1-6.
Wahrendorf J, Robra BP, Wiebelt H, Oberhausen R, Weiland M, Dhom
Effectiveness of colorectal cancer screening: results from a population-based
case-control evaluation in Saarland, Germany. Eur J Cancer
Kronborg O, Fenger C, Sndergaard O, et al.
Initial mass screening for
colorectal cancer with fecal occult blood test. A prospective randomized
study at Funen in Denmark. Scan J Gastroenterol
JD, Thomas WM, Chamberlain J, et al.
Randomised, controlled trial of faecal
occult blood screening for colorectal cancer: results for first 107,349 subjects. Lancet 1989;1:1160-1164.
Selby JV, Friedman GD, Quesenberry CP Jr, Weiss NS.
study of screening sigmoidoscopy and mortality from colorectal cancer. N Engl J Med 1992;326:653-657.
Newcomb PA, Norfleet RG, Storer BE, Surawicz TS,
Screening sigmoidoscopy and colorectal cancer mortality. J Natl Cancer Inst 1992;84:1572-1575.
Cutler JL, Ramcharan S, Feldman R, et al.
checkup evaluation study. 1. Methods and population. Prev Med 1973;2:197-206.
Dales LG, Friedman GD, Collen MF.
Evaluating periodic multiphasic health
checkups: a controlled trial. J Chronic Dis
GD, Collen MF, Fireman BH.
Multiphasic health checkup evaluation: a 16-year
follow-up. J Chronic Dis 1986;39:453-463.
Selby JV, Friedman GD, Collen
Sigmoidoscopy and mortality from colorectal cancer: the Kaiser Permanente
Multiphasic Evaluation Study. J Clin Epidemiol
Proctosigmoidoscopy and polypectomy in reducing the incidence of rectal
cancer. Cancer 1974;34:936-939.
Gilbertsen VA, Nelms JM.
of invasive cancer of the rectum. Cancer 1978;41:1137-1139.
Hertz REL, Deddish MR, Day E.
of periodic examinations in detecting cancer of the colon and rectum. Postgrad Med 1960;27:290-294.
Screening in chronic disease. New York: Oxford University Press, 1985.
Nelson RL, Abcarian H, Prasad ML.
perforation of the colon and rectum. Dis Colon Rectum 1982;25:305-308.
Waye J, Lewis B, Yessayan S.
Colonoscopy: a prospective report of complications. Gastrointest Endosc 1990;36(suppl):A226.
Colorectal cancer: the case for
barium enema. Mayo Clin Proc 1992;67:253-257.
DiSario JA, Foutch PG, Mai HD,
Pardy K, Manne RK.
Prevalence and malignant potential of colorectal polyps
in asymptomatic, average-risk men. Am J Gastroenterol 1991;86:941-945.
Winawer SJ, Zauber AG, Ho MN, et al.
Prevention of colorectal cancer by
colonoscopic polypectomy. N Engl J Med 1993;329:1977-1981.
Carroll RLA, Klein M.
often should patients be sigmoidoscoped? A mathematical perspective. Prev Med 1980;9:741-746.
Sakamoto MS, Hara JH, Schlumpberger JM.
sigmoidoscopy in a low-risk, highly screened population. J Fam Pract 1994;38:245-248.
Atkin WS, Cuzick J, Northover JMA, Whynes DK.
of colorectal cancer by once-only sigmoidoscopy. Lancet 1993;341:736-740.
Thun MJ, Namboodiri MM, Heath CW.
Aspirin use and reduced risk of fatal
colon cancer. N Engl J Med 1991;325:1593-1596.
Kune A, Kune S, Watson LF.
cancer risk, chronic illness, operations, and medications: case control results
from the Melbourne colorectal cancer study. Cancer Res 1988;48:4399-4404.
Rosenberg L, Ralmer JR, Zauber AG, Warshauer ME, Stolley PD, Shapiro S.
hypothesis: nonsteroidal anti-inflammatory drugs reduce the incidence of large-bowel
cancer. J Natl Cancer Inst 1991;83:355-358.
American Cancer Society.
for the cancer-related checkup: an update. Atlanta: American
Cancer Society, 1993.
Fleischer DE, Goldberg SB, Browning TH, et al.
Detection and surveillance
of colorectal cancer. JAMA 1989;261:580-585.
American College of Obstetricians
Routine cancer screening. Committee Opinion no. 128.
DC: American College of Obstetricians and Gynecologists, 1993.
Screening for colon cancer:
programs of the American College of Radiology. Am J Radiol 1993;160:999-1003.
American Academy of Family Physicians.
Age charts for periodic health
Kansas City, MO: American Academy of Family Physicians, 1994.
(Reprint no. 510.)
Force on the Periodic Health Examination.
Canadian guide to clinical preventive
health care. Ottawa: Canada Communication Group,
cancer overview. Cancer 1992;70:1206-1215.
Blalock SJ, DeVellis BM, Sandler
Participation in fecal occult blood screening: a critical review. Prev Med 1987;16:9-18.
Elwood TW, Erickson A, Lieberman S.
approaches to screening for colorectal cancer. Am J Public
Winchester DP, Shull JH, Scanlon EF, et al.
A mass screening program for
colorectal cancer using chemical testing for occult blood in the stool. Cancer 1980;45:2955-2958.
Occult blood screening: obstacles to effectiveness. Cancer 1992;70:1259-1265.
Winawer SJ, Miller C, Lightdale C, et al.
to sigmoidoscopy: a randomized, controlled trial of rigid and flexible sigmoidoscopy. Cancer 1987;60:1905-1908.
Petravage J, Swedberg J.
Patient response to sigmoidoscopy
recommendations via mailed reminders. J Fam Pract
affecting compliance with screening sigmoidoscopy. J
Fam Pract 1991;32:585-589.
Launoy G, Veret JL, Richir B, et al.
Involvement of general
practitioners in mass screening: experience of a colorectal cancer mass screening
programme in the Calvados region (France). Eur J Cancer
Flexible fiberoptic sigmoidoscopy: the long and the short of
it. Gastrointest Endosc 1984;30:114-116.
sigmoidoscopy: longer may not be better for the nonendoscopist. Gastrointest Endosc 1985;31:347-348.
Weissman GS, Winawer SJ, Baldwin MP, et
Multicenter evaluation of training of nonendoscopists in flexible
sigmoidoscopy. CA Cancer J Clin 1987;37:26-30.
for colorectal cancer: are we ready? JAMA
screening for colorectal carcinoma: the yield and the costs. Am J Prev Med 1985;1:18-24.
Ransohoff DF, Lang CA.
Screening for colorectal cancer. N Engl J Med 1991;325:37-41.
From the Congressional Office of
Technology Assessment: costs and effectiveness of co-lorectal cancer screening
in the elderly. JAMA 1990;264:2732.
Lynch HT, Watson P, Smyrk TC, et al.
cancer genetics. Cancer 1992;70:1300-1312.
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