GIT Kurdistan Board GEHj club interval CRC.

1. Dr. Mohamed Alshekhani
Professor in Medicine
MBChB-CABM-FRCP-EBGH
2015
1

2. Abstract:
• There is good evidence that CRC screening has been successful at
reducing both CRC incidence&death.
• Colonoscopy, utilized as either a primary screening tool or a follow-
up exam when other screening tests are positive, has significantly
contributed to these encouraging trends.
• Colonoscopy is not perfectly sensitive for detection of neoplasia &
CRC can be diagnosed within a short interval following colonoscopy
that did not detect one (Interval CRC).
• The literature surrounding these cases has rapidly expanded over
the last decade.

3. Abstract:
• The common explanations for these cancers including missed
lesions, new lesions & incompletely resected lesions.
• Current approaches to prevention largely center on consistent
adherence to quality colonoscopy standards.
• Prevention:
• Advances in technology to better visualize the colon & adequately
resect detected neoplasia.
• Improvement in training.
• Development of a culture of continuous quality improvement will
be essential to maximize the benefits of colonoscopy in daily clinical
practice.

4. Background:
• The aim of CRC screening is to reduce the risk of developing & dying
from CRC& there is good evidence that it is successful.
• The average annual incidence/mortality from CRC is declining with
22% reduction in the incidence &screening accounted for half of this
observed decline.
• CRC is a significant public health burden.
• To reduce morbidity&mortality from CRC will require expansion of
screening&improved therapeutics when disease is discovered.
• Current guidelines endorse a panel of options for screening.
• Colonoscopy is a primary screening option & the primary follow-up
exam when another modality is positive&effective colonoscopy is
critical to the success of any screening program.
• Colonoscopy is the gold standard for direct evaluation of the colon,
but it remains imperfect.

5. Background:
• Interval CRC: CRC diagnosed within a short interval following a
colonoscopy where cancer had not been detected.
• Over the last decade or so, ICRC has increased substantially.

6. Interval CRC: Definition
• Different terms:
• “Post-colonoscopy”, “missed”, “interval” CRC: describe CRC after a
colonoscopy exam that did not detect one.
• We favor “interval cancer” :Why
• 1.it is a more general term, can be used to describe similar events
when other screening modalities are being used.
• 2. Factors in addition to the “missed” lesions likely contribute.
• Interval colon: “CRC diagnosed after a screening or surveillance
exam in which no cancer is detected & before the date of the next
recommended exam.”
• “interval post colonoscopy cancer (PCCRC)” where the
circumstances (i.e., the timing of the cancer relative to the prior
recommended interval) are known.

8. PCCRC: The scope of the problem
• Establishing the scope of the problem is challenging because of
important methodological differences between studies, variably
defined as cases occurring within 36 months of colonoscopy in some
series, but significantly longer in other studies .
• interval PCCRC:2.6-9.0%(3.7%).
• A large study ( n =9,167) in adenoma-bearing population who had
all neoplastic lesions removed at baseline found that 58 individuals
were diagnosed with cancer during a median follow-up of 4 years
;6/1,000 ; 1.7 cases / 1,000 person-years of follow-up.
• A conservative estimate for interval PCCRC in an average patient
considering a screening colonoscopy is in the range of 1/1,000
colonoscopy exams, significantly > some other risks routinely
consented for(e.g. perforation)& we would recommend routinely
including this risk when obtaining informed colonoscopy consent.

9. PCCRC: Explanation
• For most cases, it is difficult to determine the precise “cause”:?
• 1.Because of unknowns surrounding tumor biology & cancer growth
rates.
• 2. There is the issue of whether a prior colonoscopy missed a cancer
or the opportunity to prevent a cancer.
• Generally, there are 3 predominant explanations:
• (1) Missed neoplasia (either cancer or significant polyps).
• (2) New lesions.
• (3) Incompletely resected lesions.

10. PCCRC Explanation: Missed lesions
• The most important contributor to interval PCCRC.
• In 58 interval PCCRCs, 30 (52%) were attributed to missed lesions.
• Optical colonoscopy missed a CRC when present ~5.3% of the time.
• In the landmark study, a 2.1-6% miss rate for adenomas ≥1 cm was
observed,with sessile / flat lesions about five times more likely to
be missed than pedunculated ones.
• Factors specifically contributing to missed flat adenomas were size,
location, bowel prep quality, withdrawal time, proficiency of the
colonoscopist.

11. PCCRC Explanation: Incomplete resection
• 19% of PCCRC due to incomplete resection.
• Incomplete resection was identified overall in 10% of polyp
resections, with higher rates observed for larger polyps & sessile
serrated polyps (SSPs)& piecemeal removals.
• 27% developed cancer in a colonic segment where a polypectomy
had been performed during the prior colonoscopy exam, but may
be de novo cancer or missed CRC in the same segment.

12. PCCRC Explanation: New lesions
• A relatively less frequent explanation, possibly accounting for about
¼ of the observed cases, because CR carcinogenesis is a lengthy
process,but this may differ between polyps sub-types(> in SSPS) ,
CRcs, ages.
• Interval cancers display the CIMP (57 vs. 33%)& microsatellite
instability (30.4% vs. 10.3%) ( 10,18,36 ), so SSPs might be the
culprit lesion in many of these cases.
• Another factor that may relate interval PCCRC & serrated polyps is
their typical proximal location in the bowel & interval cancers are
more often proximally located, although it is more difficult to reach
the right colon by colonoscopy.

13. PCCRC : Prevention
• Currently, the practice of high-quality colonoscopy is centered on:
• Adequate preparation
• Cecal intubation
• Adenoma detection.
• Proper surveillance.

14. PCCRC prevention: Bowel preparation
• Inadequate colonic cleansing likely accounts for a significant
proportion of missed lesions&often results in longer, more diffi cult
&incomplete exams&, it can also contribute to incomplete resection
if the borders of identified polyps cannot be clearly delineated.
• Suboptimal or inadequate bowel preparations may occur in a
quarter -third of patients undergoing colonoscopy.
• The single best way to improve bowel preparation is to uniformly
adopt “split-dose” or even “same-day” preparation.
• Improved patient education through high-quality educational
materials has been shown to improve bowel preparation relative to
conventional instruction specially in elderly & those with multiple
comorbid conditions.

15. PCCRC prevention: Cecal intubation
• Patients who underwent colonoscopy by endoscopists with cecal
intubations rates of ≥95% were nearly 30% less likely to be
diagnosed with a proximal interval PCCRC than those who
underwent colonoscopy by endoscopists with cecal intubation rates
<80%.
• The reasons for not accomplishing cecal intubation ;looping of the
scope&patient discomfort,more pronounced in females, as colon is
often longer & more redundant, leading to more discomfort, longer
insertion times&lower completion rates&interval PCCRC more
predominant in women.
• Currently, guidelines recommend a cecal intubation target of 90%
for all examinations & 95% for routine screening exams.
• If the exam is incomplete, re-attempts may be successful&
completion may be improved at tertiary referral centers or with
endoscopists experienced with difficult colonoscopies.

16. PCCRC prevention: Adenoma detection
• With respect to interval cancer prevention, adenoma detection rate
(ADR) is likely the single most important quality metric.
• ADRs <20% were associated with the risk of developing interval
cancer.
• interval &fatal interval cancers were 48-62% lower with ADRs >33%
compared with ADRs <19% & 3% decrease in the risk of interval
cancer for each 1% improvement in ADR.
• Targets for ADR updated with the overall target set at 25% for
screening exams &a gender-specific target of 30% for males & 20%
for females.

17. PCCRC prevention: F/U Surv recommendations
• Underutilization of colonoscopy (i.e. not bringing individuals back in
a timely manner) can facilitate the development of “new” lesions.
• Cancer survival is directly linked to the stage at diagnosis.
• Delayed examinations can have a significant impact on the success
of CRC screening & surveillance programs.
• overutilization of colonoscopy (i.e bringing individuals back earlier
than the time frame recommended) can also cause harm.
• Colonoscopy is not without risk& repeating it unnecessarily at short
intervals can directly, negatively impact the patient,drain
resources& decrease the availability of colonoscopy to those that
need it, including those that remain unscreened.
• Colonoscopy is, at times, both underutilized&overutilized&there is
good evidence that guidelines are not followed.

18. PCCRC prevention: F/U Surv recommendations
• If no adenomas are detected on an average risk screening
colonoscopy, a 10-year follow-up interval is recommended.
• if no adenomas were detected because the exam was incomplete,
performed in a patient with a poor prep, or by a provider with a
poor baseline ADR, a “successfully” applied 10-year follow-up
recommendation may do more harm than good.
• Natural language processing may become a valuable tool to support
the tracking of the accuracy of surveillance reccomendations.

20. Future direction: improved technology
• To improve mucosal inspection— particularly on the proximal
aspect of haustral folds where lesions can easily be overlooked&
3rd eye Retroscope, demonstrated modest increases in adenoma
detection
• Accessory devices to flatten folds to enhance proximal view using a
small plastic cap showed no improvement in adenoma detection.
• Balloon devices &bristles at the tip of the scope: more work in
larger populations is needed.
• Enhanced viewing of the mucosa ,the Fuse Full Spectrum Endoscopy
colonoscopy platform uses multiple contiguous video monitors fed
by additional side-facing lenses , demonstrated a significantly lower
adenoma miss rate.

21. Future direction: improved technology
• 1. it is advisable that colonoscopists know their limits when it
comes to attempting difficult polypectomies.
• Attempting but not completing polypectomy can leave behind a
scar that can make subsequent attempts even by an experienced
endoscopist more challenging.
• Tattooing lesions for subsequent removal by a more experienced
endoscopist might help, although care should be taken to avoid
injecting too near the lesion to avoid tracking into its submucosa&
the potential to adversely affect subsequent attempts.
• Evidence support the role of high magnification endoscopy to
detect residual tissue &using argon photocoagulation to reduce
recurrence when resecting large polyps in a piecemeal manner.

22. Future direction: training&QA programes
• Improve the training of the colonoscopy technique & quality
assurance of those individuals or programs providing it.
• Prior training of the endoscopist (e.g., gastroenterology vs. surgery)
has been associated with interval cancer &highlights its importance
& with training, ADR can imprve.
• A real culture of quality assurance/improvement is needed to move
practice forward.
• Quality assurance work requires measurement, assessment&
follow-up to determine whether change has occurred &durable.
• Developing the appropriate expertise within practices to
continuously monitor & improve colonoscopy is critical to
preventing interval PCCRC & maximizing the benefit of CRC
screening programs.

23. CME Qs:
• 1. A 66-year-old female presents for her first screening colonoscopy. She has a
history of chronic constipation, current tobacco use, T2DM& medically
complicated obesity (BMI 35.4 kg/m2). Her pre-procedure vital signs were
stable& propofol sedation was used. During the procedure, cecal intubation was
documented by photographs of the appendiceal orifice, terminal ileum& ICV.
Bowel preparation was fair. During the withdrawal phase of the exam, she
develops a loud sonorous breathing pattern&her O2 saturation drops below 90%,
possibly due to sleep apnea. One 6-mm sessile suspected adenoma is resected
quickly by cold snare in the descending colon. Upon completion of her
colonoscopy, her O2 saturation is >92%. Your withdrawal time for the procedure
was 4 minutes & 15 seconds.
• Which one of the following factors is the strongest contributor to her risk of
developing an interval colorectal cancer?
• A. Obesity
• B. Tobacco abuse
• C. Low colonoscopic withdrawal time
• D. Incomplete resection of the descending colon polyp

24. CME Qs:
• 2. A 74-year-old female with depression schedules a surveillance colonoscopy.
Her last colonoscopy was performed 3.5 years ago, during which a 18-mm tubular
adenoma was resected from her ascending colon in a piecemeal fashion. Full
dose PEG was utilized to prepare for this procedure& bowel preparation was fair.
Today, her vital signs are stable& her physical examination is unremarkable. Due
to consistently poor colon preparation for prior procedures, her endoscopist now
routinely utilizes split-dose PEG for all colonoscopies. Which one of the following
potential measures would most likely increase the likelihood of identifying
adenomas during this procedure?
• A. Documenting cecal intubation by ICV photographs
• B. Increasing colonoscopic withdrawal time
• C. Provision of high quality educational materials geared to improve colon
preparation
• D. Utilization of narrow band imaging

25. CME Qs:
• 3. An ambulatory endoscopy center has developed a quality improvement task
force to improve patient safety / quality of colonoscopy performed in their unit.
Adenoma detection rates, cecal intubation rates& overall colonoscopic
preparation quality are measured&reported for each endoscopist privileged to
perform colonoscopy in the unit. The task force decides to update the informed
consent form with emerging data regarding patient risk for the development of
colorectal cancer between a normal screening colonoscopy& a follow-up
examination. Noting that multiple studies vary significantly, they decide to
reference the Nurses’ Health Study & the Health Professional’s Follow-Up Study.
Based on this study, what data should they use to describe approximate interval
colorectal cancer development risk after a negative screening colonoscopy?
• A. 20 cases of colorectal cancer per 1,000 colonoscopies
• B. 0.7 cases of colorectal cancer per 1,000 colonoscopies
• C. 1 case of colorectal cancer per 100 colonoscopies
• D. 5 cases of colorectal cancer per 1,000 colonoscopies