8.  Screening for Colorectal Cancer



RECOMMENDATION



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



Colorectal 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.1 An individual's lifetime

risk of dying of colorectal cancer in the U.S. has been estimated to be

2.6%.2 About 60% of patients with colorectal cancer have regional or

distant metastases at the time of diagnosis.1 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.2 The average

patient dying of colorectal cancer loses 13 years of life.2 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.3,4 Familial

syndromes are estimated to account for 6% of all colorectal cancers,3 and

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 risk was 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 hisory.4b Diets high in

fat or low in fiber may also increase the risk of colorectal cancer.3



Accuracy of Screening Tests



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.3



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.5-10 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,11 and

gastric irritants such as salicylates and other antiinflammatory

agents,12 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.13,14 Other causes of false-negative results include heterogeneous

distribution of blood in feces,15 ascorbic acid and other antioxidants that

interfere with test reagents,16 and extended delay before testing stool

samples.17



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.6,5,9,18-

20 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.21 This large 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.22,23 Rehydration of stored slides can improve

sensitivity, but this occurs at the expense of specificity.24 In one 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.5



Other tests have been proposed to improve the accuracy of screening for

fecal 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.9,10,25-29 Recently developed hemoglobin

immunoassays offer the promise of improved sensitivity and specificity

but require further evaluation before being considered for routine

screening.30,31



The third screening test for colorectal cancer is sigmoidoscopy.

Sigmoidoscopic screening in asymptomatic persons detects 1-4 cancers

per 1,000 examinations.32,33 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,34-37 the length

of the sigmoidoscope has a direct effect on case detection. The rigid

sigmoidoscope, which has an average depth of insertion of about 20 cm38-

44 and allows examination to just above the rectosigmoid junction,45 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 examinations46,47 with the capability of

detecting 65-75% of polyps and 40-65% of colorectal cancers48-52

Researchers have examined the feasibility of introducing a 105-cm

flexible sigmoidoscope in the family practice setting,53 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.54



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,55 but only 2-3% have colorectal

cancer.56-58 Depending on the type of adenomatous polyp, an estimated 5-

40% eventually become malignant,59 a process that takes an average of

10-15 years.60,61 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 reach.20,21 Colonoscopy, which 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.21

Some retrospective studies have reported a higher sensitivity of barium

enema for detecting colorectal cancer (about 90-96%),62,63 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.2

Since there 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

mortality.



Two of these trials5,6 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 per 1,000).5 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,64 but the assumptions in the analysis have been

disputed by the authors.65 Another controlled trial,6 which 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.66,67 Three large

clinical trials of FOBT screening, currently under way in Europe, are

expected to report their results in the coming years.7,68,69



Recent case-control 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.70 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.71



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 cancer.72-74 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.75 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.76-78 However, both studies lacked internal controls and used

nonrandomized methods to select participants; other methodologic

problems with these investigations are outlined in other reviews.75,79



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 examinations.20,21,32,80 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,5,81 and the risk of serious bleeding is 1 in 1,000.5 The

estimated risk of perforation during barium enema is 1 in 5,000-10,000

examinations.82



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.48,49,83 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.84

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.21



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

FOBT5 and over age 45 for sigmoidoscopy.70 Theoretically, the potential

yield from screening should increase beyond age 50 since the incidence of

colorectal cancer after this age doubles every 7 years.2 Modeling studies

suggest that beginning screening at age 40 rather than at age 50 offers no

improvement in life expectancy.21 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.21 Another model suggested that an interval of 2-4 years would

allow detection of 95% of all polyps greater than 13 mm in diameter.85 In

a case-control study, the risk reduction associated with sigmoidoscopy

screening did not diminish during the first 9-10 years after

sigmoidoscopy.70 Other studies suggest that a single sigmoidoscopic

screening examination may be adequate for low-risk individuals,86 an

approach being investigated in the United Kingdom.87



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 colon cancer.88-90



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 50.91 Similar

recommendations have been issued by the American Gastroenterological

Association,92 the American Society for Gastrointestinal Endoscopy,92

and the American College of Obstetricians and Gynecologists.93 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.21 The

American College of Radiology recommends screening with barium enema

every 3-5 years as an equivalent alternative to periodic sigmoidoscopy.94

The recommendations of the American Academy of Family Physicians are

currently under review.95 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.96 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.



Discussion



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 study97

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

cancer is the ability of patients and clinicians to comply with testing.

Patients may not comply with FOBT for a variety of reasons,68,98 but

compliance rates are generally higher than for sigmoidoscopy. Recent

clinical trials report compliance rates of 50-80% for FOBT among

volunteers,5-7,68,69 but lower rates (about 15-30%) have been reported

in community screening programs.99-101 Although the introduction of

flexible fiberoptic instruments has made sigmoidoscopy more acceptable

to patients,102 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%).103 In a study in which

sigmoid-oscopy was recommended repeatedly, only 31% of participants

consented to the procedure,72-74 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,104,105 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.33 In addition, examinations using

60-cm sigmoidoscopes are more time-consuming35-39 and require more

extensive training106-108 than do those using shorter instruments.



Another 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 $200.22,109 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.109 Others

have calculated that FOBT screening alone could cost the United States

and Canada between $500 million and $1.2 billion each year.110,111

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.112 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.



The downstream 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.65 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.



The special 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).4,113 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.



CLINICAL INTERVENTION



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

determined.



     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 colon cancer, 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 patients.



The draft update of this chapter was prepared for the U.S. Preventive

Services Task Force by Steven H. Woolf, MD, MPH.



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