|Colorectal Cancer (CRC); Computed Tomographic
Colonography (CTC); Optical Colonoscopy (OC)
|Colorectal Cancer (CRC) is the third most common type of cancer
and the second leading cause of cancer death in the United States . In
2011, an estimated 141,000 cases of colon and rectal cancer and 49,000
deaths are expected, accounting for 9% of all cancer deaths in the U.S.
Over the last two decades there has been a decline in CRC cancer rates
of approximately 2.8% per year (in males) and 2.7% per year (in females)
which reflects improvement in early detection and treatment. Clinical
evidence amassed over the last several decades indicates that routine
CRC screening, compared to no screening, detects CRC at an earlier
stage, and reduces the incidence of CRC by interrupting the adenomato-
carcinoma sequence in colon polyps through colonoscopy-guided
polypectomy and thus reduces CRC mortality. When CRC is detected in
an early, localized stage, the five year survival rate is 90%. However, only
39% of all CRC is diagnosed at this stage, in part due to the underuse
of screening . After CRC has spread regionally to involve adjacent
organs or lymph nodes, the five year survival rate decreases to 70%;
when the disease has spread to distant organs, the five year survival
rate is only 12%. Interestingly, in contrast to the overall CRC incidence
decline, among adults younger than 50 years, for whom screening is not
recommended for those at average risk, CRC incidence rates have been
increasing by 1.6% per year since 1998 .
|The U.S. Preventive Services Task Force (USPTF) recommends
screening for colorectal cancer using fecal occult blood testing,
sigmoidoscopy, or colonoscopy in adults, beginning at age 50 years and
continuing until age 75 years . Recently, Computed Tomographic
Colonography (CTC) has been evaluated for its potential in CRC
|Screening for CRC
|Prior to the late 1960’s, barium enema was the primary means of
evaluating the entire colonic luminal surface. Rigid sigmoidoscopy was
used for removal of distal polyps and surgery for more proximal larger
lesions, usually those greater than 2 cm diameter. The first colonoscopic
polypectomy was performed in 1969; thereafter, the rapid development
of flexible colonoscopes from 1970-90 made it possible to directly
examine the entire colonic mucosal surface and to safely remove polyps without opening the abdomen . With the realization that most
colon cancers develop from adenomatous colon polyps , effective
preventive strategies require both accurate detection and a means
for safe, efficient polyp removal. Although Double Contrast Barium
Enema (DCBE) and sigmoidoscopy are established methods for polyp
detection, DCBE provides no means for polyp removal and misses over
half of polyps, one cm or greater . Because sigmoidoscopy views only
the left side of the colon, it is estimated to miss half of all advanced
neoplastic disease . Thus, while CRC screening guidelines include
fecal occult blood testing, fecal immunochemical testing, flexible
sigmoidoscopy, colonoscopy, barium enema and CTC, there has been
an understandable shift towards Optical Colonoscopy (OC) as the most
commonly recommended screening test for CRC and the standard for
surveillance of patients at high risk for CRC [7-11]. A recent report
from the 2006-2007 National Survey of Primary Care Physicians
Recommendations and Practices for Cancer Screening shows that in
the year 2000, fecal occult blood and flexible sigmoidoscopy were the
most commonly recommended CRC screening tests, but by 2007 these
were supplanted by OC .
|Standard Optical Colonoscopy (OC)
|Most colon cancers are thought to arise from adenomatous polyps
which over a period of years evolve into true malignancies . Thus,
detecting and removing such polyps prior to their progression to frank
malignancy should reduce cancer occurrence. Though there are no
randomized controlled studies showing that colonoscopy reduces the incidence of colon cancer, strong evidence for the effectiveness of OC
in preventing cancer was reported in the National Polyp Study .
In this study, 1418 patients were followed for an average of 5.9 years
after the removal of one or more adenomas by colonoscopy. Comparing
the incidence of CRC in the study patients with rates of CRC in three
index groups, there was a 76% to 90% reduction in CRC . Another
large case-control study showed similar reduction of CRC (66%) in
patients who had colonoscopy in the preceding ten years . Thus,
with acceptable procedure times, complication rates, and the ability to
find and remove polyps, it appears that OC offers an effective means
for interrupting the adenoma-to-carcinoma evolution of polyps and
decreases the incidence of CRC.
|Flexible fiberoptic colonoscopy or Optical Colonoscopy (OC)
has evolved to a routine 20-30 minute procedure. The test requires a
pre-procedure preparation consisting of low residue foods and colon
cleansing usually with oral, large-volume polyethylene glycol lavage
the day prior to the examination . Intravenous sedation, vital sign
monitoring, and a 2-3 hour post-procedure recovery are also required.
Though OC is considered by most to be the gold standard for viewing
the colonic surface, it has limitations. In the largest studies of patients
referred for a wide range of suspected colonic problems, failure to view
the entire colon occurs in 3-9% and 3% of screening examinations [16-21].
|OC complications consist mainly of perforation, bleeding,
and cardiovascular events (Table 1). Rates vary depending on the
population studied. Studies of screening OC in asymptomatic patients
report major complications in 0.2- 0.3% [22,23]. A large retrospective
study of non-screening colonoscopies found an overall incidence
of complications of 0.5% with 0.08% in patients without biopsy or
polypectomy and 0.7% in patients with biopsy or polypectomy .
In a prospective study of surveillance and screening colonoscopies, the
pooled incidence of angina, myocardial infarction stroke or transient
ischemic attack was 0.14% . The rates of perforation in a large study
of screening colonoscopies was 0.01%  and a study of colonoscopies
done in ambulatory endoscopy centers in a mixed population a showed
perforation rate of 0.03% . While some studies have found no
difference in perforations rates with or without polypectomy ,
when studied in some detail, most authors feel that perforation rates
increase with polypectomy as reported in the study by Levin et al.
 who found an overall perforation rate of 0.09% with 0.06% in
patients without and 0.11% in patients with biopsy or polypectomy. As
for bleeding, a large study of Medicare patients identified significant
bleeding in 0.21% of patients having screening OC procedures and
0.87% of patients with polypectomy , while Levin found bleeding
occurred in 0.48%, all of which had biopsy or polyp removal , but
no bleeding in patients without biopsy or polypectomy. Death rates for
all causes within 30 days have been noted as 0.07% but 0.007% when
reported as specifically related to OC .
|Advances in optical colonoscopy techniques
|Factors such colon tortuosity, diverticular disease, observer inexperience and haste, may limit visualization of the entire colon
mucosal surface by OC resulting in adenoma miss rates as high as
15-32% . Of particular concern are small or flat lesions which in
some studies show prevalence of up to 9% and are suspected of having
higher predilection for harboring malignancy [30,31]. For this reason,
endoscope makers have developed high-definition optics to improve
the operator’s ability to detect subtle mucosal contour changes. To date,
such scopes have not consistently proven to be superior to standard
equipment, though there is some evidence that they help in detecting
small (1-5 mm) adenomas [29,32].
|Chromoendoscopy is a technique of colonoscopically inspecting
the colonic mucosa after staining it with dyes such as indigo carmine
or methylene blue. Studies using this technique to look for subtle
contour changes demonstrate improved rates of adenoma detection
. Chromoendoscopy has been combined with improvements in
optics such as imaging magnification to observe staining patterns for
predicting tissue malignant potential. A randomized, prospective trial
of 660 patients comparing this high-definition chromoendoscopy and
standard OC showed that chromoendoscopy improved sensitivity
for colorectal lesions (both neoplastic and non-neoplastic) of 6-10
mm from 90% to 97% and specificity from 61% to 100% .
Though chromoendoscopy has not come into general use because the
procedure is technically cumbersome, with continued improvement
in colonoscopic optics and wider dissemination of tissue staining
techniques, chromoendoscopy may eventually play a role in detecting
colonic mucosal neoplastic changes.
|Computed Tomographic Colonography (CTC)
|Over the last ten years, Computed Tomographic Colonography
(CT colonography or CTC) has become a new minimally invasive and
safe approach to CRC screening, providing structural evaluation of
the entire colorectal mucosal surface without colonoscopic intubation.
Initially described by Vining  and applied clinically by Hara et al.
, CTC has gained momentum as a best alternative test to traditional
optical colonoscopy as has been suggested by a large landmark clinical
trial by Pickhardt et al.  and a multi-center study trial conducted
by the American College of Radiology Imaging Network (ACRIN) 
demonstrating its effectiveness. This is further supported by two recent
reports from European studies of CTC [39,40].
|Recently, CTC has been advocated by several American
professional medical societies as an effective alternative to conventional
colonoscopy for CRC screening and is now included on the American
Cancer Society’s list of approved colorectal screening options .
However, despite these achievements, challenges to the widespread
clinical dissemination of CT colonography for detection of colorectal
cancer remain, including the need for approval and coverage by CMS.
|The reported advantages of CTC are reduced procedure time,
fewer complications, and avoiding the need for conscious sedation.
With these advantages, a high quality CTC program can be used as
a compliment to conventional optical colonoscopy for improving the low rates of CRC screening currently observed. However, the goal of
achieving consistently accurate lesion detection requires close attention
to quality control with critically important technical, procedural,
professional and interpretational requirements.
|Elements of a quality CTC program
|Early CTC studies showed wide variability in sensitivity and
specificity for polyp detection [41,42] emphasizing the need for
including the following critical elements for a credible, high-quality
CTC program: 1) fastidious attention to the preparation of the patient,
including adequate colon cleansing, stool tagging and optimal colon
insufflation; 2) high-quality, non-contrast, CT imaging with acquisition
of single breath hold, thin section slices on multislice CT scanners
in the prone and supine positions; 3) dedicated 2D and 3D image
reconstruction and display software; 4) adequate time for reading
studies (average of 20 min in the ACRIN study); 5) ready availability
of same-day colonoscopy back up for patients requiring polypectomy;
and, 6) high quality, intensive reader training and tracking of reader
performance. Our standard is a three day bowel preparation as outlined
in the Appendix; we do not use I.V. contrast during CTC.
|Similar to optical colonoscopy, CT colonography interpretation
is reader dependent and highly reliant on the operator’s training
and experience. Generally, recommended reader training consists
of at least 50-75 colonoscopically verified polyp-rich cases using
dedicated workstations, high quality 2D and 3D reconstruction and
display capability with immediately available expert feedback [43,44].
However, a recent study of reader training, suggests that to achieve
adequate accuracy for patients in a CTC screening program, a test set
population more nearly matching the smaller, less frequent numbers of
polyps may require more than 160 cases for adequate reader training
. In addition, it is currently recommended that reader competence
be reviewed every two years with at least 50 unknown cases . Of
note, recently, some studies have suggested that Computer-Aided
Detection (CAD) as a second reader, may help, particularly novice
readers, increase sensitivity with relative small sacrifices in specificity
and time to read [45,46].
|Complications of CTC
|Though CTC appears to have fewer complications than OC, it is not
complication-free, the greatest risk being that of colonic perforation.
In a survey of over 21,000 patients from 16 US medical centers with
wide experience in CTC, the reported incidence of perforation was
0.009% with each of the two complicated cases being done with manual
insufflations of room air. However, a study from the UK reported 9
perforations in 17,067 CTC’s, five of which were symptomatic and one
of which required laparotomy. The other four were asymptomatic noted only at CTC. Thus, the symptomatic perforation rate (the rate that is the
most meaningful for comparison to that of OC) was 0.03%.
|Of the nine complications, causes were found in four including
inadvertent intubation of a rectal stump, forceful catheterization,
coexistent ulcerative colitis, and an obstructing sigmoid cancer. It
should be noted that the patients in the UK study vs. the US study
tended to be older which may at least in part explain the differences
between the reported perforation rates. Other factors that appear to
increase the risk of perforation, include, symptomatic colonic disease,
previous deep colonic biopsy, and manual insufflation of room air.
Factors decreasing risk are young, screening patients and pressurecontrolled
insufflation with CO2 .
|Controversies regarding screening for colorectal cancer by
|Accuracy of polyp detection by CTC: Comparison with OC:
One debated aspect of CTC is how best to quantify its accuracy. Two
accepted methods of analysis are the “per patient” and the “per polyp”
detection rates. The “per polyp” method describes the accuracy of CTC
to find all polyps in an individual undergoing the screening study. The
“per patient” analysis evaluates the number of patients with at least
one polyp of significant size (typically greater than 5 mm) detected.
This metric is more clinically relevant because, regardless of the total
number of polyps present, if only a single significant polyp is detected
on CTC, the patient will undergo a subsequent colonoscopy where
all polyps, including those not detected on CTC, would be removed.
Thus, the determination of a minimal polyp size on CTC for which
colonoscopy can be recommended is central to the potential success of
CTC as a screening examination.
|Another difficulty in evaluating the efficacy of CTC is that the “gold
standard” in most comparative studies is optical colonoscopy. Yet it is
known that colonoscopy is not a perfect test (Table 2). Van Rijn reviewed
six studies totaling 465 patients who had “tandem” OC procedures, where
patients had a baseline OC followed by a second OC on the same day
and found miss rates of 21% for all polyps, and 2.1% of adenomas 10
mm or greater . Heresbach  recently reported on 286 patients in a
multi-center prospective trial of such tandem OC’s and found a per polyp
miss rate of 28% of all polyps, 20% of all adenomas, 11% of advanced
adenomas, and 9% of adenomas 5 mm or greater . Because these
comparative studies had no independent gold standard, there is a small
chance that a true polyp determined to be present on a CT colonography
may be missed on OC simply due to the limitations of the latter study.
Thus, with colonoscopy being an imperfect “gold standard” some lesions
classified as false positives on CTC might be prevalent lesions missed by
colonoscopy which underestimate the sensitivity of CTC.
|Using methods including state-of-the-art patient preparation,
scanning and image analysis as well as a method of “segmental
unblinding”, Pickhardt et al. established a separate gold standard by
which sensitivities of both CTC and OC could be determined .
By this means, each patient underwent CTC followed by OC on the
same day. The gold standard was established by performing sequential
withdrawal of the colonoscope in colon segments. The scope was first
passed to the cecal tip. After examining by withdrawal from the cecum, a
second observer revealed the results of the CTC exam for that segment.
If there was disagreement between the CTC and the initial OC exam,
the colonoscope was passed back into the cecum to establish a true gold
standard finding. Next, the scope was withdrawn into the ascending
colon and so on. In this manner, sensitivities were determined for both
OC and CTC. Examining 1233 patients with this protocol, the per
patient sensitivity of OC was 87.5, 91.5, and 92.3% for polyps 10, 8 and
6 mm largest diameter respectively; the per patient sensitivity for CTC
was 93.8, 93.9, and 88.7%. Thus, the established sensitivities of both OC
and CTC were comparable for polyps 10 mm in size and OC missed
about 10% of adenomatous polyps 6 mm and greater in size, about the
same number as the tandem colonoscopy studies had shown [31,48,50].
|While Pickhardt’s study showed excellent sensitivities and
specificities using uniform methods for performing CTC in a small
group of readers, a larger multi-center trial with 15 participating
centers was recently reported by the American College of Radiology
Imaging Network (ACRIN) . In this study, 2531 asymptomatic
patients scheduled to have screening OC patients also had CTC
examinations with OC as the gold standard. CTC readers had to
demonstrate they had read at least 500 CTC examinations or had
to pass a test demonstrating 90% sensitivity in finding 10 mm
polyps in a training examination. Segmental unblinding was not
used. The results demonstrated CT colonography had per patient
and per polyp sensitivities to polyps 10 mm or greater of 90% and
84% respectively. Thus, CTC identified 90% of subjects with polyps
10 mm or more in diameter (Table 3). Recently, an Italian multicentered
trial in 1103 patients considered high risk for CRC showed CTC to have an 85.3% sensitivity for detecting advanced neoplasia
of 6 mm or larger with 87.5% specificity .
|Meta-analysis studies [52-55] have reported per patient CTC
sensitivities of 82-88% for polyps 10 mm or greater and specificities
of 95-97%, but with more varied sensitivities for polyps in the 6-9
mm, and 5 mm or smaller range (63-84% and 48-65%, respectively).
Limitations of these analyses include wide variations in numbers of
patients, scanners, scanning technique, reader training, and patient
preparation (Table 4).
|In summary, the reported data from the largest trials evaluating CTC
suggest: (1) CTC can detect polyps 10 mm or greater with sensitivities
comparable to that of optical colonoscopy; (2) CTC specificity has
consistently averaged 90% or above; (3) CTC is not sensitive to polyps
5 mm and smaller; AND, (4) CTC sensitivity to polyps 6-9 mm have
a wider range of variation between studies, but in the best studies
where there has been detailed attention to the highest quality in reader
training, patient preparation, scanning, image display, and adequate
time for reader interpretation, CTC approaches the sensitivity of OC.
|The "Less-Than-Ten-Millimeter" Polyp Conundrum –
How Should Small Polyps be Managed?
|Standard practice for optical colonoscopy in a CRC screening
program is to remove all polyps. If CTC is the screening modality
used, robust algorithms for polypectomy referral become critical in
preventing development of CRC. The specifics of such algorithms
depend on determining the likelihood of malignant potential in any
given polyp detected by CTC. To date, judging malignant potential
relies almost exclusively on polyp size. While there is general agreement
that large polyps (10 mm or greater) should be referred for removal,
there is controversy about the management of polyps less than 10 mm.
As noted above, studies have shown comparable sensitivities for OC
and CTC (>90% in the best studies) for detecting polyps greater than 10
mm diameter (Tables 3 and 4) [31,37,38,48]. However, with the several
studies reporting a wider range of CTC sensitivity for medium sized (6-9 mm) polyps and low sensitivity for small (5 mm and less) polyps,
there is controversy regarding CTC’s role in managing polyps less than
ten millimeters in diameter.
|Studies of polyp histology in patients referred for OC and CTC
suggest that small polyps represent a low malignant potential with
two recent studies [56,57] showing the percentage of such polyps
having advanced histology ranging from 0.87-1.7% and the incidence
of cancer 0.03-0.05%. While the natural history of such polyps is not
yet clear, some studies suggest that very few of these lesions progress
to malignancy and some have been documented to regress. Hofstad
performed serial colonoscopies to follow polyps less than one cm for
three years and found that 25% of adenomas were unchanged in size,
40% grew, and 35% regressed . Other studies have suggested that
the transformation to malignancy is relatively slow with the National
Polyp Study estimating that it takes an average of 5.5 years for a 10 mm
polyp to transform into cancer [13,59].
|A decision analysis study by Pickhardt  estimated a 10 year risk
of developing CRC in small (5 mm or less) polyps of 0.08%, medium
sized (6-9 mm) of 0.7% and large (10 mm or more) of 15.5%. The study
suggested that small polyps could be ignored, large polyps should be
referred for prompt colonoscopic removal and patients with 6-9 mm
polyps followed with surveillance CTC. With these points in mind, the
current CTC reporting guidelines, listed in table 5, state that reporting
polyps 5 mm and smaller is not necessary [43,60,61].
|However, with imperfect knowledge of the natural history of
medium and small polyps, there remains controversy regarding the
management of polyps <10 mm, especially 6-9 mm. While early studies
of 6-9 mm polyps showed 3.4% advanced histology with no cancers,
two more recent, large studies of polyp histology have shown that 59-
67.5% is adenomas with 5.3-6.6% showing advanced histology and up
to 0.2% invasive cancer [56-58]. Lieberman reviewed the histology of
polyps from 13,992 screening colonoscopies (Table 6) and projected that if these patients had initially been evaluated by CTC instead of
OC, using the ACR referral algorithm (Table 5) for management, one
in 15 screening patients with a single largest polyp of 6-9 mm would
have advanced histology, but by CTC guidelines would have CTC
surveillance in three years rather than prompt colonoscopic resection
. Similarly, Rex reviewed the histology of polyps from 10,034
colonoscopies and projected that if current CTC criteria had been used,
about 30% of patients with high-risk adenoma findings would have had
studies interpreted as normal and another 18-23% would be offered
CTC surveillance at three years rather than prompt polypectomy .
|Current CTC guidelines suggest colonoscopic polypectomy for
polyps 10 mm or greater and three or more 6-9 mm polyps. For fewer
than three 6-9 mm polyps, patients are offered prompt colonoscopic
removal or 3-year CTC surveillance, and there is evidence that most
patients and physicians choose colonoscopic removal . At present,
with the low probability that polyps 5 mm and less will proceed to
malignancy, most guidelines agree these can be ignored. However with
the uncertainty of knowing the natural history of small polyps, some
authors modify their reporting to include polyps 5 mm or less and if
greater than three in number to consider a follow-up CTC in three
|CTC Radiation Dose Considerations
|In 2008, the United States Preventive Services Task Force rated
CTC “indeterminate” as a CRC cancer screening test because of
uncertainty regarding long-term implications of radiation exposure
and the potential financial and clinical implications arising from the
identification of extracolonic findings . The long-term impact of
CTC examination doses of 5-10 mSv per study is generally felt to be
inconsequential  but, when a radiographic examination is used for
population-based screening, this issue must be strongly considered
when advocating for serial use of this test to screen healthy populations.
When extracolonic abnormalities (such as aortic abdominal aneurysm,
hepatic masses, or renal masses) are identified on CTC, additional
diagnostic testing, perhaps invasive, could add substantial cost and
burden to individuals and to society. Those advocating and performing
CTC must ensure that the examination does not result in the workup of
excessive numbers of incidental or benign findings.
|The "Extracolonic Findings" Conundrum
|Incidental Extracolonic Findings (ECFs) may be defined as findings
on CTC that have potential serious health effects and are asymptomatic,
unsuspected, and unrelated to the colon. Because CTC is generally done
without intravenous contrast material and using low radiation dose,
the ability to definitively characterize incidental findings is limited and
some ECFs categorized as potentially important are likely to eventually
be diagnosed as having no significant effect on the patient’s health.
Studies performed primarily to test the effectiveness of CTC have also
evaluated the frequency of ECFs [65-68]. Heterogeneous populations,
varying definitions of incidental findings, and the nature of ECF
assessment limit comparison of individual data. However, one systemic
review by Xiong et al.  of prior publications reported that 2.7% of
3280 patients in the combined series had extracolonic cancers including
6 renal cell carcinomas, 5 ovarian carcinomas, 4 pancreatic carcinomas
and 1 liver cancer. Only 1% of these were considered to be early stage.
Approximately 1% of patients had abdominal aortic aneurysms. Older
and symptomatic populations were more likely to have “important”
ECFs. Approximately 1 in 100 patients undergo invasive procedures for
ECFs following CTC and costs are higher for populations with higher
risk subjects [66,68].
|In studies assessing the cost effectiveness of CTC screening for
CRC, the costs and benefits of evaluating ECFs have been reported.
A study conducted by Hassan et al.  reported the greatest relative
benefit from detecting ECFs on CTC was a decrease in deaths from
abdominal aortic aneurysms, rather than from incidentally discovered
extracolonic cancers. Overall, large populations undergoing CTC
screening for CRC may be expected to diagnose 2% of these patients with
early extracolonic malignancies and 1.9% with significant aneurysms.
While the range of reported incidental findings, including important
and unimportant findings may be up to 50% of patients undergoing
CTC, “important” findings range from 7-12%. Estimates of the cost
of examining and treating patients because of incidental findings also
vary. However, studies that assessed both initial diagnostics costs and
downstream diagnostic and treatment costs of ECFs indicated average
added expenditures ranging from $28 to $297 [67-69], representing
large costs in a small percentage of the population averaged over the
entire population. Longitudinal studies are needed to determine the
long-term clinical outcomes and the potential benefits and harms
associated with the spectrum of extracolonic diseases and conditions
that become evident with CTC.
|Cost Effectiveness Considerations for CRC Screening
|With ongoing discussions about modifying the health-care system in
the United States, much emphasis is placed on comparative effectiveness
research to inform reimbursement levels. Cost-effectiveness studies show
that all screening strategies are better than no screening, but there is no
agreement on which strategy is the best . Small differences in baseline
assumptions such as sensitivities for the detection of polyps, rates of
adherence to any particular strategy, variations in procedure costs,
practice patterns and resource capacity can greatly influence conclusions.
While both OC and CTC have repeatedly been shown to be effective in
detecting CRC, OC appears to be only marginally cost-effective and CTC
is not yet clearly cost effective . However, recent cost effectiveness
comparisons of OC and CTC in a hypothetical Medicare population
showed CTC to be more cost effective than OC when the power of CTC
to screen for abdominal aortic aneurysm was included in the analysis
. In another cost-effectiveness study, Knudsen  showed that if the
availability of CTC enticed 25% of otherwise unscreened individuals in
the Medicare population to be screened, CTC would be cost effective at a
cost estimate of $488 (2010 dollars).
|If properly implemented in multi-modality disease prevention and
screening setting, CTC provides an appealing alternative to traditional
optical colonoscopy for CRC screening in populations unwilling or
unable to undergo colonoscopy, thus potentially increasing CRC
screening rates and reducing CRC incidence and mortality. For
operator-dependent tests – flexible sigmoidoscopy, CT colonography
and optical colonoscopy – advanced operator training and experience
improve practitioner performance. Certification, quality standards,
and minimal volume requirements also optimize outcomes and,
therefore, sensitivity. Assuring high-quality optical endoscopy and CT
colonography should be part of all screening programs. Because several
screening approaches have similar efficacy, efforts to reduce colon cancer
deaths should focus on implementing multidisciplinary strategies that
maximize the number of individuals who undergo screening of some
type. The different options available to screen for CRC are variably
acceptable to patients and eliciting preferences will improve adherence
through shared decision making that incorporates information on local
test availability and quality as well as patient preference.
|CTC is clearly not a replacement for colonoscopy; polypectomy
via colonoscopy remains the primary modality for preventing CRC
development; many individuals eligible for screening may prefer the
“one-stop shop” approach of colonoscopy. Ideally, these two tests will
be used in a complimentary fashion in high quality comprehensive
colorectal screening programs where attention to excellence in quality
of examination performance and interpretation and multidisciplinary
approaches and collaborations are employed.
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