Complete polyp resection rate of colorectal polyps: long follow-up study

In recent years several studies have been published about colorectal interval
carcinomas, carcinomas that develop in patients who have had colonoscopic
surveillance. Three major causes for interval carcinomas have been described.
In 50-80% of the cases, interval carcinomas result from missed lesions at
previous colonoscopy. Several tandem studies have reported a substantial
adenoma miss rate of 20-26%, and approximately 2-12% for polyps larger than
10mm.Another cause of interval cancers could be that these carcinomas have an
aggressive biologic behaviour, for example the association with microsatellite
instability.
A third cause of interval colon carcinomas are incompletely removed lesions.
These manifest as cancers that arise at the site of the colon where during
previous colonoscopy a polyp was resected. Only a small number of studies have
evaluated the incidence of interval cancers caused by incomplete resection,
with percentages varying from 10-27%. Farrar et al found a significant
association between the location of the polypectomy sites within a segment and
the subsequent location of the interval carcinoma. However it is hard to draw
strong conclusions about the subject because of the small size of studies on
the subject. Besides that, it is difficult to determine whether a cancer occurs
at the site of a previously identified premalignant lesion or whether it merely
occurred in the same colon segment because of limited descriptive information
on adenoma location in colonoscopy reports. Carcinomas arising from
incompletely resected polyps highlights the deficiencies in technique and
adequate assessment of resection margins. Especially large adenomas that
require piecemeal resection are a high risk for incomplete resection. Given the
major consequences for patients of failed detection or inadequate removal of
neoplastic lesions, systematic evaluation of cancer occurrence after
colonoscopy seems the best way to improve patient outcome. However, this can
only be studied retrospectively, after the interval carcinoma already
developed. A better way to discover the true adequacy of radicality in
polypectomy is to directly examine the polypectomy site.
Few studies have evaluated the presence of residual adenomatous tissue by
histological assessment of forceps biopsies obtained from the polypectomy site.
Complete resection rates vary between different polypectomy techniques, from
40% with cold biopsy forceps to almost 90% with snare polypectomy. A recent
study from Pohl et al described an overall incomplete resection rate of 10%,
which increased for large polyps and for sessile serrated adenomas/polyps. One
great disadvantage of the study method used in these studies, is the bias
created by the endoscopist obtaining biopsies from his own polypectomy site.
Ideally these biopsies would be obtained by a different endoscopist or during
follow-up colonoscopy after the surveillance interval. Also, participating
endoscopists were aware of the study design and are could be more focused to
ensure complete resections of the polyps.
We aim to test the incomplete resection rate of polypectomies in patients
during surveillance colonoscopy after previous polypectomy, and we will compare
this rate for different sized polyps.

To compare the percentage of incompletely resected polyps during colonoscopy
for polyps sized 1-4 mm, 5-9 or 10-20 mm.

Screening participants with a positive FIT and symptomatic patients between the
age of 50-75 years will undergo a colonoscopy. During colonoscopy all detected
polyps will be removed as usuall, but only one polyp per segment will be
included: the most proximal polyp per segment. Contra lateral of the
polypectomy site a single tattoo will be placed to locate the polypectomy site.
Per colonic segment only 1 tattoo will be placed, regardless of the number of
polyps per segment. After 1, 3 or 5 years, depending on the advised
surveillance interval according to the Dutch gastroenterology guidelines,
patients will receive a surveillance colonoscopy. The location of previous
polypectomy will be detected with help of the tattoo. If a residual polyp is
found, treatment as usual will be performed. If no optical residual is found,
several biopsies will be taken at the polypectomy site. Histopathological
evaluation of the residual polyp will be compared with previous histopathology.
Histopathological evaluation of the biopsies will show if the polypectomy at
initial colonoscopy was complete or that microscopic residual polypoid tissue
was found.

Patients in our study will receive 1 to max.3 tattoos in the colon. The ink we
will use (SPOT) for marking the polypectomy site, has been used for many years
in colonoscopy practice.1 No side-effects of SPOT have been described in the
literature, in contrast to the earlier used ink.1 Patients with suspected
colorectal cancers diagnosed during colonoscopy will be excluded from the study
and no tattoos for the purpose of the study will be placed. If a tumour is not
seen during intubation and a polyp has been removed and marked proximally but a
tumour is unexpectedly found distal of the polyp, the patient will be excluded.
Because the patient has now two markings of the colon, correct location of the
tumour during surgery might be difficult. Because of this risk, we will
extensively describe both tattoos and tumour localization with added endoscopic
images. We will also personally inform the surgeon.
Patients will be under close surveillance and from multiple studies we know
that occurrence of colorectal cancer in a surveillance population is small.
During the surveillance colonoscopies biopsies of the former polypectomy site
will be taken. In every case colonic biopsies are accompanied by a minimal risk
of perforation, bleeding and infection. These complications are cited in the
written patient information.