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Clinical guidelines

Guidelines for preventive activities in general practice 9th edition

9.2 Colorectal cancer

Average risk

Age 0-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-79 > 80

High risk

Age 0-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-79 > 80

Biennial faecal occult blood test (FOBT) can reduce colorectal cancer (CRC) mortality by 16%.17 The original trials of FOBT screening used the guaiac-based FOBT but this has been superseded by the more sensitive and specific faecal immunochemical test. Organised screening by FOBT is recommended for the asymptomatic (average risk) population from 50 years of age every two years (A) until 75 years of age with repeated negative findings.18,19

Increased risk is determined by family history; this should include determining the number of relatives affected by CRC, side of family and age at diagnosis. DRE is not recommended as a screening tool (D), but is important in evaluating patients who present with symptoms such as rectal bleeding.

Colonoscopy is not recommended as a screening test for people at average risk of CRC. No randomised controlled trials (RCTs) have evaluated the effect of colonoscopy on CRC mortality, although trials are in progress in Spain, Sweden and the US. Colonoscopy has indirect and direct harms, including, rarely, death from the procedure (1 in 10,000–14,000 colonoscopies).20,21 Harm may be caused by the bowel cleanout prior to the procedure (eg dehydration and electrolyte imbalances), the sedation used during the procedure (eg cardiovascular events), or the procedure itself (eg infection, colonic perforations, bleeding). There is insufficient evidence about the use of computed tomography (CT) colonography (also refer to Chapter 15. Screening tests of unproven benefit), faecal deoxyribonucleic acid (DNA) or plasma circulating DNA tests to recommend them as alternatives to FOBT for CRC screening.22 There is insufficient evidence to recommend the use of low-dose aspirin in people at average risk of CRC.23

Table 9.2.1. Colorectal cancer: Identifying risk
Who is at risk?What should be done?How often?
Category 1 – Average or slightly increased risk
Asymptomatic people with:
  • no personal history of bowel cancer, colorectal adenomas, inflammatory bowel disease or family history of colorectal cancer (CRC)
  • one first-degree or second-degree relative with CRC diagnosed aged ≥55 years
Faecal occult blood test (FOBT; I, A) Every two years from 50 years of age (Practice Point) 17, 19, 24
Category 2 – Moderately increased risk (1–2% of the population)
Asymptomatic people with:
  • one first-degree relative with CRC diagnosed aged <55 years
  • two first-degree or one first-degree and one second-degree relative(s) on the same side of the family with CRC diagnosed at any age (without potentially high-risk features as in Category 3)

Sigmoidoscopy plus double-contrast barium enema or computed tomography (CT) colonography (performed by an experienced operator) are acceptable if colonoscopy is contraindicated

Consider offering FOBT (III, B)
Every five years from 50 years of age, or at an age 10 years younger than the age of first diagnosis of CRC in the family, whichever comes first (Practice Point) 19, 25, 26

In intervening years
Category 3 – High risk (relative risk of ~4–20%; <1% of the population)*
Asymptomatic people with 25,26:
  • three or more first-degree or second-degree relatives on the same side of the family diagnosed with CRC (suspected Lynch syndrome, also known as hereditary non-polyposis CRC [HNPCC]or other Lynch syndrome-related cancers†
  • two or more first- or second-degree relatives on the same side of the family diagnosed with CRC, including any of the following high-risk features
    • multiple CRC in the one person
    • CRC aged <50 years="" li="">
    • a family member who has or had Lynch syndrome-related cancer
  • at least one first-degree or second-degree relative with CRC, with a large number of adenomas throughout the large bowel (suspected familial adenomatous polyposis [FAP])
  • somebody in the family in whom the presence of a high-risk mutation in the adenomatous polyposis coli (APC) or one of the mismatch repair genes has been identified
Refer for genetic screening of affected relatives

Refer to bowel cancer specialist to plan appropriate surveillance (III, B)

FAP: flexible sigmoidoscopy


Colonoscopy in attenuated FAP‡

HNPCC: – colonoscopy

Consider offering FOBT (III, B)
Those at risk for:
  • FAP (no APC mutation defined): Every 12 months from 12–15 to 30–35 years of age and every three years after 35 years of age#
  • Lynch syndrome: one to two yearly from 25 years of age or five years earlier than the youngest affected member of the family (whichever is earliest)

Aspirin 100 mg/day is effective prophylaxis§
somebody in the family in whom the presence of a high-risk mutation in the adenomatous polyposis coli (APC) or one of the mismatch repair genes has been identified HNPCC: – colonoscopy In intervening years
Members of proven FAP|| and Lynch syndrome families who are shown not to carry the family mutation are no longer at high risk and revert to the average-risk group and still require population-based screening Consider offering FOBT (III, B) (Practice Point)
*Age of starting screening varies in high-risk groups: 25 years of age for those with Lynch syndrome or five years earlier than the earliest age of onset in the family

†Lynch syndrome-related cancers include colorectal, small bowel, endometrial, ovarian, gastric, brain and urothelial cancers

‡Attenuated FAP is characterised by a significant risk for colon cancer but fewer colonic polyps (average of 30), more proximally located polyps, and diagnosis of CRC at a later age. Patients with 10–100 adenomas have an attenuated form of FAP, which can be due to APC mutation (dominantly inherited) or MUTYH bi-allelic mutations (recessive). In each case the CRC risk is high

§Aspirin at 600 mg/day reduced Lynch syndrome cancer incidence by 50–68% in the Colorectal Adenoma/Carcinoma Prevention Programme 2 (CAPP2) trial.27 Follow-up of the low-dose aspirin randomised controlled trials (RCTs)28, 29 suggests low-dose aspirin (100 mg/day) also reduces cancer incidence by half. A dose–response RCT in Lynch syndrome is open for recruitment at

||FAP is an autosomal disorder caused by a germline mutation in the APC gene. APC mutation, as manifested by the development of CRC, approaches 100% by 50 years of age in untreated subjects. FAP, however, accounts for less than 1% of all CRC cases. HNPCC (Lynch syndrome) is due to an inherited mutation (abnormality) in a gene that normally repairs the body’s DNA. Both disorders have an autosomal dominant mode of transmission within families and carry a very high risk for cancer. As the HNPCC gene mutation is present in every cell in the body, other organs can also develop cancer. In untreated FAP, mutation carriers have a lifetime risk for CRC close to 100%. In HNPCC, the risk for colorectal or other syndrome cancers is 70–90% 19

#Bi-annual (six-monthly) or annual sigmoidoscopy for APC gene carriers of diagnosed FAP (colonoscopy in attenuated FAP)

APC, adenomatous polyposis coil; CAPP2, Colorectal Adenoma/Carcinoma Prevention Programme 2; CRC, colorectal cancer; CT, computed tomography; FAP, familial adenomatous polyposis, FOBT, faecal occult blood test; HNPCC, hereditary non-polyposis colorectal cancer; RCT, randomised controlled trials

Patients who have adenomatous polyps removed at colonoscopy are then at above-average risk for the development of metachronous adenomatous polyps and CRC. Table up of people after polypectomy. It is important to try and obtain information about the histology, size and number of polyps removed as this determines the future risk of adenomas and CRC, and therefore frequency of recommended surveillance colonoscopy.30

Table 9.2.2. Follow up after polypectomy
Polyp type and numberRecommended colonoscopy screening interval
Small pale distal hyperplastic polyps only (not adenomas) No follow up required as no increased risk of metachronous colorectal neoplasia
One to two small tubular (<10 mm) adenomas Repeat colonoscopy at five years

If that colonoscopy is normal, repeat colonoscopy at 10 years or faecal occult blood test (FOBT) every two years
High-risk adenomas (three or more adenomas, ≥10 mm, or with tubulovillous or villous histology, or high-grade dysplasia) Three-year intervals
Large and sessile adenomas removed piecemeal Three to six months and again at 12 months to ensure complete removal
Multiple adenomas, which is a strong determinant of risk of metachronous advanced and non-advanced neoplasia:
  • ≥5 adenomas
12 months
Multiple adenomas, which is a strong determinant of risk of metachronous advanced and non-advanced neoplasia:
  • ≥10 adenomas
Sooner than 12 months (because of the likelihood of missed synchronous polyps)
Family history in addition to adenomas Intervals determined by adenoma characteristics, unless a syndromic risk mandates more frequent surveillance
If advanced adenomas are found during subsequent surveillance Three-yearly schedule is prudent, but the choice should be individualised. The interval can be lengthened if advanced adenomas are not found
People aged >75 years No surveillance as lead time for progression of an adenoma to cancer is around 10–20 years
FOBT, faecal occult blood test
Table 9.2.3. Test to detect colorectal cancer
Faecal occult blood test (FOBT) screening Two main types of FOBT are available: Guaiac and faecal immunochemical tests 31, 32

Immunochemical tests are preferred as they have greater sensitivity and higher uptake (A).31 Two or three serial stools should be tested, depending on the type and brand of test being used. Follow the manufacturer’s instructions

It is essential that any positive FOBT (including just one of the samples) is appropriately investigated by colonoscopy (such people being at least 12 times more likely to have colorectal cancer [CRC] than those with a negative test). With guaiac tests, even if a subject fails to follow dietary restrictions, it is dangerous to assume that a positive result is a result of dietary non-compliance
CRC, colorectal cancer; FOBT, faecal occult blood test



Measures to increase screening in these groups include organised approaches such as employing recall and reminders;32,33 recommendations by the GP for the screening;33,34 addressing capacity issues, including convenience;33,35 and minimising barriers such as cost.33,35,36 Refer to the RACGP’s Putting prevention into practice: Guidelines for the implementation of prevention in the general practice setting (Green Book)

The National Bowel Cancer Screening Program, using a faecal immunochemical test, is being expanded and by 2020 will offer biennial screening for people aged 50-74. GPs are critical, not just in maximising participation, but managing participants with a positive FOBT.34,37

Participation is under-represented by Aboriginal and Torres Strait Islander, and culturally and linguistically diverse (CALD) peoples.38


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