- 1 Definition
- 2 Background
- 3 Evidence
- 3.1 Systematic review evidence
- 3.2 Overview of additional evidence (non-systematic review relevant literature)
- 4 Evidence summary and recommendations
- 5 Health system implications
- 6 References
- 7 Appendices
The low risk category refers to 1–2 small (<10mm) tubular adenomas without high-grade dysplasia (HGD).
For surveillance intervals for clinically significant serrated polyps with synchronous low risk conventional adenomas see First surveillance intervals following removal of serrated polyps (± conventional adenomas)
The 2011 edition of this guideline recommended surveillance at 5 years for individuals following removal of 1–2 small (<10mm) tubular adenomas without HGD, although recognising that the risk of metachronous advanced neoplasia (MAN) in this group was likely to be no greater than that of the average population. The 2018 recommendations are based on systematic review, non-systematic review of relevant literature, international recommendations and expert opinion.
What should be the first surveillance interval following removal of low risk conventional adenomas only? [SAD1]
Systematic review evidence
The systematic review included studies published since 2010 of colonoscopy procedures performed from 2002. The evidence base for low-risk individuals, particularly high quality studies with long-term outcomes, using modern endoscopy technique, is limited (see Technical report). Data relating to surveillance colonoscopy in patients with low-risk adenomas were reported from one level III-2 prospective cohort analysis of a randomised controlled trial, four level II prospective cohort studies and nine level III-2 retrospective cohort studies. Six cohort studies had a low risk of bias, one a moderate risk of bias and seven a high risk of bias.
Outcomes reported included incidence and risk of metachronous colorectal cancer (CRC), metachronous adenoma (MA) and metachronous advanced adenomaAn adenoma that measures 10mm or more in size. Includes adenomatous polyps greater than or equal to 10 mm in size or with a significant villous component or with high-grade dysplasia. (MAA). The 11 cohort studies reporting incidence of metachronous cancer and advanced adenomaAn adenoma that measures 10mm or more in size. Includes adenomatous polyps greater than or equal to 10 mm in size or with a significant villous component or with high-grade dysplasia. tended to fall within the 3–5 year surveillance range. Studies tended to report incidence of cancer closer to 5 years. No included studies reported follow up at 10 years or mortality. There was consistency in the outcomes of metachronous CRC and MAA, but not MA. Most studies were from Asian populations not necessarily directly generalisable, but probably applicable to the Australian population. The incidence of metachronous CRC, reported in 11 studies, was ≤1% in all studies.
The incidence of MAA, reported in 11 studies with surveillance intervals of 3–5 years, ranged from 1.35–8.04% in 10 of these studies.Back to top
Overview of additional evidence (non-systematic review relevant literature)
Long-term follow up from earlier studies
Four level III-2 studies included long term outcomes in groups of low risk patients but were not included in the systematic review as they did not fit the criteria, particularly as they included colonoscopies performed prior to 2002.
Two level III-2 studies reported long-term CRC incidence:
- Cottet et al reported on a French retrospective cohort (n=5779). Participants had incident adenomas removed between 1990 and 1999 and were followed up using registry data until 31/12/2003, for a median of 7.7 years (inter-quartile range 5.2–10.5). The standardised incidence ratio for CRC was 0.68 (0.44–0.99) regardless of surveillance colonoscopy. The 10-year cumulative probability of CRC was 0.76% (0.39–1.48) with surveillance colonoscopy and 1.37% (0.70–2.65) without surveillance colonoscopy.
- Brenner et al performed a large case-control study in Germany, identifying cases of CRC (n=2582) and matched controls (n=1798) from the population registry. Patients who had undergone a colonoscopy with removal of a polyp without high risk features had a reduced adjusted odds ratioA comparison of the odds (probability) of something happening in one group with the odds of it happening in another. (OR) of CRC at any site, proportional to time since polypectomy: 0.2 (0.1–0.2) for <3 years, 0.4 (0.2–0.6) for 3–5 years and 0.8 (0.4–1.5) for 6–10 years, compared with no colonoscopy (OR 1.0).
Two level III-2 studies reported CRC-specific mortality:
- Zauber et al compared CRC-specific mortality in participants (n=2602) who had low- and high-risk adenomatous polyps removed in the National Polyp Study between 1980 and 1990 with standardised incidence-based CRC-specific mortality in the general population using data from the US Surveillance Epidemiology and End Results (SEER) program. The proportion of participants with non-advanced adenomas was 43%, with 81% having 1–2 adenomas only. Median follow-up was 15.8 years, with maximum of 23 years. Overall, the standardised mortality rate (SMR) was 0.47 (0.26–0.80, p=0.008). The risk of CRC mortality of those with adenomas removed was the same as those with non-adenomatous polyps at 10 years. Cumulative CRC-specific mortality at 20 years was 0.8% for the National Polyp Study patients, compared with 1.5% in the general population (significance level not reported). Mortality reduction was similar for the first 10 years of follow-up at 0.44 (0.14–1.06, p=0.09) compared with 10 or more years at 0.49 (0.23–0.93, p=0.04).
- Løberg et al followed n=40,826 individuals after adenoma removal from between 1993 and 2007 and compared CRC-specific mortality with the general population up to 2011, with a median follow-up of 7.7 years (maximum 19 years). In those with low-risk adenomas who did not undergo any surveillance colonoscopy, as per Norwegian guidelines, the SMR was 0.75 (0.63–0.88).
Diminutive adenomas (defined as <6mm) are of great interest due to their increased detection with high-quality endoscopy.
It was reported in a Chinese study that the incidence of MAA following removal of diminutive adenomas was 1.8% and small adenomas 3.2%, compared with 3.1% in those with no adenomas at baseline, at follow-up between 1 and 5 years.
The risk of MAA among patients undergoing first follow-up colonoscopy after removal of adenomas <10mm was assessed in an Israeli study (median follow-up 32 months), a hazard ratioA measure of how often a particular event happens in one group compared to how often it happens in another group, over time. of 3.49 (1.6–7.6) was reported in small adenomas compared with diminutive adenomas.
Comorbid metabolic syndromeMetabolic syndrome is a collection of conditions that often occur together and increase the risk of diabetes, stroke and heart disease.
The influence of the metabolic syndromeMetabolic syndrome is a collection of conditions that often occur together and increase the risk of diabetes, stroke and heart disease. on MAN is increasingly recognised, with consistent evidence showing that it increases risk. The risk is greatest following the removal of low risk adenomas at baseline colonoscopy and in males. There are many definitions of metabolic syndromeMetabolic syndrome is a collection of conditions that often occur together and increase the risk of diabetes, stroke and heart disease.. According to the most commonly used definition, that of the US National Cholesterol Education Program Adult Treatment Panel III, three or more of the following are required:
- Abdominal obesity: waist circumference ≥102cm in men and ≥88cm in women
- Hypertriglyceridemia: ≥1.695mmol/L
- Low HDL-C: <2.2mmol/L in men and <2.8mmol/L in women
- High blood pressure (BP): >130/85mmHg
- High fasting glucose: >6.1mmol/L.
Clinical practice guidelines from other countries
Many countries have published recommendations for surveillance after adenoma removal (Table 4) and most classify polyps as being either low or high risk. However, there is an increasing trend to further stratify risk. The US-Multi Society Taskforce guidelines endorsed by the American Gastroenterological Association (AGA) 2012 include the low risk category as 1–2 tubular adenomas <10mm without HGD, and recommended a surveillance interval of 5–10 years for patients with low-risk polyps. Recent commentaries have called for a clear message advocating screening for this group according to the strategy for the average-risk population, and advocating consideration of risk-profiling to stratify patients within the low-risk group. As average-risk screening differs between countries, the actual recommendation can also differ.
The Canadian Association of Gastroenterology (CAG) guidelines have the same definition of low risk as the AGA, with a recommendation for return to average-risk screening (colonoscopy at 10 years in Canada) unless there are personal or familial risk factors that increase risk, in which case a colonoscopy at 5 years is appropriate. The European Society of Gastrointestinal Endoscopy guidelines 2013 have the same definition of low risk as the AGA and CAG, with a clear surveillance recommendation for the low-risk group of returning such patients to a screening programme (if present in the individual country) or a screening colonoscopy at 10 years. This is similar to the low-risk group in the European guidelines developed by the International Agency for Research on Cancer. New Zealand national guidelines use the same low-risk definition and recommend clinicians to consider a colonoscopy at 5 years.
The British Society of Gastroenterology guidelines, which take into consideration the UK National Institute for Health and Clinical Excellence recommendations, are the only guidelines to define low risk differently and purely on the basis of size. All adenomas <10mm in size, regardless of dysplasia and villosityThe state of being villous, a histopathological feature of some tubular adenomas. Villous adenoma is a type of polyp found in the colon or rectum that appear as a cauliflower-like mass., are considered ‘low-risk’ and the recommendation for surveillance is either no surveillance or, in the presence of other factors, to consider colonoscopy at 5 years.
In Norway, follow-up is not recommended in the low-risk group, 1–2 adenomas, >75 years of age, hyperplastic polyps and no remaining adenomas/remnants or unknown histology. A 5-year surveillance interval is recommended for those with ≥3 adenomas or 1–4mm adenomas left in situ.
Løberg et al recently published long-term SMR data from a Norwegian registry of n=40,826 patients who had had adenomas removed. The number of adenomas and histology was available, but size was not. Even with a strategy of ‘no surveillance’, the low-risk group had a CRC-specific SMR of 0.75 (0.63–0.88).
The Dutch surveillance programme has undergone two changes. The most recent recommendations from 2013 are based on the work of van Heijningen and use a risk score range of 0–5, incorporating number of adenomas, size ≥10mm, villosityThe state of being villous, a histopathological feature of some tubular adenomas. Villous adenoma is a type of polyp found in the colon or rectum that appear as a cauliflower-like mass. and proximal location. Recommendations are no surveillance for those with a risk score of 0, surveillance at 5 years for those with a risk score of 1–2, and surveillance at 3 years for those with a risk score of 3–5.
Summary of international guidelines
Based on the best available evidence, expert international guidelines agree that, following removal of 1–2 small (<10mm) tubular adenomas without HGD, most individuals are at no greater risk of CRC than the general population.
Recommendations worldwide include no surveillance colonoscopy or return to average-population screening in many cases, with colonoscopy at an interval of 10 years where screening colonoscopy is used. In the Australian context, average risk population screening would be faecal occult blood testA test that can detect microscopic amounts of blood in stools. as per the National Bowel Cancer Screening Program (NBCSP).
The importance of high-quality colonoscopy is recognised, as is the fact that there may be a sub-group who will benefit from a surveillance interval of 5 years, with intervals of 5–10 years accordingly recommended. In the British guidelines, patients with 1–2 adenomas <10mm with villous and HGD are also included in the low-risk group with a similar recommendation.
Evidence summary and recommendations
|The incidence of metachronous colorectal cancer following removal of low-risk conventional adenomas only was ≤1%, with the majority of studies performing surveillance at 3–5 years.||II, III-2||, , , , , , , , , |
|Incidence of any adenoma following removal of low-risk conventional adenomas only ranged from 27.48% to 53.48% amongst the nine cohort studies reporting this outcome. Surveillance intervals mainly ranged between 3 and 5 years.||II, III-2||, , , , , , , |
|The incidence of metachronous advanced adenomas following removal of low-risk conventional adenomas only ranged from 1.35% to 8.04% with a surveillance interval of 3–5 years in 10 of 11 studies that reported this outcome.||II, III-2||, , , , , , , , , |
Low-risk individuals – conventional adenomas only
First surveillance intervals should be no sooner than 5 years following the complete removal of low-risk conventional adenomas only (1–2 small [<10mm] tubular adenomas without high-grade dysplasia).
Low-risk individuals – conventional adenomas only
First surveillance interval of 10 years is appropriate for most individuals following complete removal of low-risk conventional adenomas only (1–2 small [<10mm] tubular adenomas without high-grade dysplasia).
Consistently high-quality colonoscopy is imperative for optimal cost effectiveness and for implementation of uniform surveillance guidelines.
Polyp/adenoma size as per the endoscopist documentation should be used for determining surveillance intervals. All endoscopists should ensure size measurements are accurate using a reference standard (eg an open biopsy forceps or snare).
Surveillance intervals should be determined after the colon has been cleared of all significant neoplasia, once histology is known and in the context of individualised assessment of benefit to the patient.
A shorter surveillance interval of 5 years could be considered for men who fit the criteria for the metabolic syndromeMetabolic syndrome is a collection of conditions that often occur together and increase the risk of diabetes, stroke and heart disease., because they may have increased risk of metachronous advanced neoplasia following removal of low-risk adenomas.
Return to the National Bowel Cancer Screening Program with a faecal occult blood testA test that can detect microscopic amounts of blood in stools. after 4 years, is an appropriate option and should be discussed with the patient.
Patients with 1–2 diminutive (<6mm) low-risk adenomas have a very low risk of metachronous neoplasia and should be returned to the NBCSP after 4 years unless there are significant extenuating factors.
Individuals with a significant family history of colorectal cancer should be assessed according to current Australian clinical practice guidelines for the prevention, early detection and management of colorectal cancer (see Risk and screening based on family history) in addition to these recommendations, and the shorter interval used.
Notes on the recommendations
The systematic review evidence does not support colonoscopy within 5 years but does not offer guidance for longer intervals. Evidence from general literature review indicates that the long-term risks of CRC and of CRC-specific mortality are similar to, or lower, than those of the general population following removal of 1–2 small (<10mm) tubular adenomas without HGD based on studies from an era of lesser quality colonoscopy. The risk is even lower for diminutive adenomas. Risk is likely to be further reduced in the current era of high quality colonoscopy.
Based on the best available evidence, expert international guidelines agree that following removal of 1–2 small (<10mm) tubular adenomas without HGD, most individuals are at no greater risk of CRC than the general population.
Health system implications
These surveillance guidelines will result in substantial change to which health care providers will need to adjust. Table 3 and colour-coding in this section aims to facilitate transition from the old to new guidelines. An educational program and simple decision aids, such as wall charts and online decision tools, would help healthcare provider become familiar with the recommendations for surveillance intervals. These could be developed, promoted and distributed in conjunction with the relevant professional bodies and healthcare providers in the public and private domains.
The management of surveillance following removal of adenomas is critical in terms of health outcomes, demand for colonoscopy and cost. Recently, the Cancer Research Division, Cancer Council NSW used the Australian developed and validated model Policy1-Bowel to compare the new and previous surveillance guidelines specifically related to the National Bowel Cancer Screening Program. Preliminary results demonstrate comparable health outcomes, reduced number of surveillance colonoscopies and similar program-related costs (see the preliminary results report on the Modelled comparison of proposed surveillance recommendations for the NBCSP).
There is likely to be an increased cost for pathologic assessment if a substantial proportion of health care providers do not currently submit all polyps removed for pathologic assessment or do not separate specimens.
Barriers to implementation
The main barriers to implementation of these recommendations will be dissemination across Australia and familiarisation for healthcare providers. This will be facilitated by a coordinated implementation and evaluation program.
Table 3. Summary of recommendations for first surveillance intervals following removal of conventional adenomas only Back to top
Table 4 Summary of international surveillance guidelines
|10Y (or routine screening)||5Y||3Y||1Y|
|Australian (2011)||1–2 small (<10mm) tubular adenomas without HGD||3–4 adenomas
≥10mm with HGD or villosityThe state of being villous, a histopathological feature of some tubular adenomas. Villous adenoma is a type of polyp found in the colon or rectum that appear as a cauliflower-like mass.
|AGA (2012)||No polyps or small (<10mm) hyperplastic polyps in the rectum or sigmoid||3–10 tubular adenomas
Villous or HGD
|>10 adenomas (<3Y)|
|1–2 small (<10mm) tubular adenomasa|
|SSP <10mm with no dysplasia||SSP ≥10mm OR with dysplasia OR
|Serrated polyposis syndrome|
|Canadian (2013)||1–2 small (<10mm) tubular adenomas with LGDb||3–10 tubular adenomas
|SSA <10mm with no dysplasia||SSP≥10mm OR with dysplasia OR
traditional serrated adenoma
|Serrated polyposis syndrome|
|ESGE (2013)||1–2 small (<10mm) tubular adenomas with LGDc||≥10mm
|Serrated <10mm with no dysplasia||Serrated ≥10mm or dysplasia|
|1–2 small (<10mm) adenomasd||3–4 small (<10mm) adenomas
|≥5 small adenomas
≥3 adenomas with at least one ≥10mm
|European (2010)||1–2 tubular adenomas <10mm, LGD||3–4 adenomas
|New Zealand (2012)||1–2 tubular adenomas <10mm, LGD (consider)e
Consider at 5Y
|1–2 adenomas ≥10mm
3–4 adenomas <10mm
3–4 adenomas if ≥10mm
|Korean (2012)||1–2 small (<10mm) tubular adenomas, LGD||Villous, HGD,
|Dutch (2013)||PRS 0||PRS 1–2||PRS 3–5|
|PRS: one point each for: 2–4 adenomas, size ≥10mm, villous histology, proximal location; two points if ≥5 adenomas|
|Norwegian (1996)||No routine surveillance if:
1–2 small tubular adenomas with LGD
Age >75 years
No remaining adenomas/remnants or unknown histology
1–4mm adenomas left in situ
|10 years if:
|Japanese (2014)||Follow-up colonoscopy should be repeated within 3 years after polypectomy|
|Chinese||No recommended surveillance guidelines|
|AGA: American Gastroenterological Association; BCSP: [UK] Bowel Cancer Screening Programme; BSG: British Society of Gastroenterology; ESGE: European Society of Gastroenterology; HGD: high-grade dysplasia; HPP: hyperplastic polyp; LGD: low-grade dysplasia NICE: National Institution of Clinical Excellence; PRS: personalised risk score; SSP: sessile serrated polyp; TSA: traditional serrated adenoma; Y: year(s).
aGuideline states: ‘The evidence supports a surveillance interval of longer than 5 years for most patients’. bGuideline states: ‘Clinicians may want to individualise the surveillance interval based on adenoma size, family history and patient preference. There are data suggesting that 10 years may be appropriate for most individuals’. cGuideline states: ‘Surveillance is not indicated in the low risk group’. dGuideline states: ‘Consider at 5 years if age, comorbidity, family history, accuracy and completeness of examination relevant’ eGuideline recommends clinicians consider surveillance colonoscopy at 5 years for this group.
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|PICO question SAD 1||Evidence statement form SAD1||Systematic review report SAD1|