It is recognised that the risk of bowel cancer varies with the type and number of polyps found at colonoscopy. Not all
bowel polyps have the potential to become malignant and not all patients who have been found to have polyps will go on to
have recurrent polyps and therefore an increased risk of bowel cancer.1, 2 The general aim is that surveillance
should be performed at the minimum frequency required to reduce morbidity and mortality from bowel cancer.1 This
should be balanced against the risks of harm from colonoscopy, such as any psychological distress or complications of the
procedure, and also against the financial impact to the health system (and potentially to individuals).1 Other
evidence-based interventions, such as smoking cessation, a reduction in the consumption of red/processed meats and the use
of aspirin, should be discussed with patients.1, 3
In 2020, updated New Zealand guidance was published for people post-colonoscopy who have had complete removal
of adenomas or serrated polyps to address the variation in the intervals required for follow-up (Table 1).2 Two
factors influenced the new advice:
- That some groups of patients with adenomas have a low risk of colorectal cancer in the future
- That there is a risk of colorectal cancer with some serrated polyps
Table 1: Surveillance intervals based on findings at high-quality colonoscopy. Adapted from 2020
“Update on polyp surveillance guidelines” with expert advice from the NBCWG.2
| 1 year |
3 years |
5 years |
10 years or NBSP
(whichever comes first) |
Adenomas*
≥ 10 adenomas** |
Adenomas*
5 – 9 adenomas < 10 mm
Adenoma ≥ 10mm
Tubulovillous adenoma or Villous adenoma
Adenoma with HGD |
Adenomas*
3 – 4 adenomas < 10 mm |
Adenomas*
l – 2 adenomas < 10 mm |
Serrated polyps*
Serrated polyposis syndrome – initial interval after polyp clearance** |
Serrated polyps*
≥ 5 SSL < 10 mm
SSL ≥ 10 mm
SSL with dysplasia
Traditional serrated adenoma |
Serrated polyps*
l – 4 SSL < 10 mm
HP ≥ 10 mm† |
|
*If there are both adenoma < 10 mm and SSL < 10 mm, the numbers should be summed up
and follow-up interval for SSL should be applies
†A 3-year follow-up interval is favoured if concern about consistency in distinction between sessile serrated
lesion and hyperplastic polyp locally
**Consider referral to the NZ Familial Gastrointestinal Cancer Service (NZFGCS), see referral criteria
below |
NBSP: National Bowel Screening Programme
SSL: Sessile serrated lesion (= sessile serrated adenoma/polyp)
HGD: High grade dysplasia
HP: Hyperplastic polyp |
Inflammatory bowel disease (IBD) is associated with an increased risk of development of bowel cancer. The risk can be
classified as low, intermediate or high, largely reflecting the extensiveness and level of activity of the two main forms
of IBD, either ulcerative colitis or Crohn’s disease.4
Recommendations from 2012, state that:4
- A baseline colonoscopy and biopsies as appropriate should be performed 8 – 10 years after a definitive diagnosis of
IBD
- Ongoing surveillance with colonoscopy should be offered depending on the patient’s level of risk:
- Low risk: colonoscopy at five years
- Intermediate risk: colonoscopy at three years
- High risk: colonoscopy at one year
N.B. For those at intermediate or high risk, the intervals can be extended to five years provided there have been two
consecutive colonoscopies that show quiescent disease with no dysplasia, and no other risk factors (i.e. family history,
a stricture or primary sclerosing cholangitis).
For information about surveillance in people with a family history of bowel cancer, refer to the first article
in this series: “Referral of patients with features suggestive of bowel
cancer: Ministry of Health guidance"
