Bowel cancer

National Guide to preventive healthcare for Aboriginal and <br/>Torres Strait Islander people

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National Guide

Cancer | Bowel cancer

Dr Jonathan Gillies

Key messages

Risk factors such as cigarette smoking, alcohol consumption, exercise and dietary factors account for approximately 50% of the incidence of all bowel cancers.¹
Primary care is well placed to help reduce the incidence and mortality from bowel cancer by promoting and assisting healthy ways of living.
The National Bowel Cancer Screening Program (NBCSP) is an effective and publicly funded population-based program using two-yearly immunochemical faecal occult blood testing (iFOBT) to detect early abnormalities and asymptomatic bowel cancer.²
Updated clinical practice guidelines (September 2023), which have been implemented in the NBCSP, recommend screening of individuals every two years from age 45–74 years.³
Screening participation is increased with encouragement and access to testing kits from healthcare providers.⁴
Individuals with a family history of bowel cancer require an assessment of their level of risk for screening, prevention and surveillance recommendations.⁵

Recommendations

Screening

Type of preventive activity - Screening
Who/target population	What	When	Strength of recommendation	Key source(s) and reference(s)	Rationale/key considerations informing recommendation
All people aged 45–74 years without symptoms or family history (average risk)	Encourage participation in iFOBT screening	Every two years	Strong	National guideline³	Screening for bowel cancer using the iFOBT has demonstrated population-level health benefits
All people who complete an iFOBT	Make sure results and outcomes for everyone who completes an iFOBT, including referral for colonoscopy, are registered with the NCSR	Every two years	Good practice point	National guideline³	The NCSR provides prompts for screening and follow-up to participants, so it is important for healthcare providers to notify the NCSR when NBCSP screening is initiated by the health service/practice or when NBCSP screening should be deferred if screening has occurred outside the program
All people in Category 1 (higher risk but less than twice average; see Box 1 )	Encourage eligible patients to complete and return the iFOBT home test kit from the NBCSP Provide alternative access to the iFOBT home test kits by bulk ordering and issuing kits directly to eligible patients through the NCSR (see Useful resources)	Every two years	Strong	National guideline⁵	Colonoscopy screening is not warranted in a population with a weak family history given the yield of clinically significant lesions at screening with colonoscopy is low
All people in Category 2 (two- to fourfold higher than average risk; see Box 1)	Colonoscopy (or computed tomography colonography if colonoscopy is contraindicated) Genetic testing is not recommended at present for people with Category 2 risk	Every five years starting at 10 years younger than the earliest age of diagnosis of bowel cancer in a first-degree relative or age 50 years, whichever is earlier, to age 74 years If eligible, people should use the NBCSP before their elevated risk is identified or colonoscopy screening is required	Good practice point	National guideline⁵	As per guideline
All people in Category 3 (risk at least fourfold and up to 20-fold higher than average; see Box 1)	Referral to a genetic service for consideration of further testing	As clinically indicated every five years starting at 10 years younger than the earliest age of diagnosis of bowel cancer in a first-degree relative or age 40 years, which every is earlier, to age 74 years If eligible, people should use the NBCSP before their elevated risk is identified or colonoscopy screening is required	Good practice point	National guideline⁵	As per guideline

Behavioural

Type of preventive activity - Behavioural
Who/target population	What	When	Strength of recommendation	Key source(s) and reference(s)	Rationale/key considerations informing recommendation
All people (eg from adolescence onwards)	Provide health risk factor counselling and primary prevention messages regarding diet (including high fibre intake and minimising foods such as red and processed meat), healthy weight, physical activity, tobacco smoking and alcohol (refer to Chapter 2: Healthy living and health risks, Healthy eating, Physical activity and sedentary behaviour, Smoking and Alcohol and Chapter 15: Overweight and obesity)	Opportunistically	Good practice point	National guideline³	Preventive health opportunity Approximately 50–60% of all bowel cancers could be prevented by these factors⁴
All people who complete an iFOBT and follow-up	Make sure results and outcomes for everyone who completes an iFOBT, including referral for colonoscopy, are registered with the NCSR (see GP assessment report in the Useful resources)	As clinically indicated	Strong	National guideline³	The NCSR provides results and prompts for screening and follow-up to participants, so it is important for healthcare providers to notify the NCSR when screening and follow-up are initiated by the health service/practice outside of the NBCSP

Medication

Type of preventive activity - Medication
Who/target population	What	When	Strength of recommendation	Key source(s) and reference(s)	Rationale/key considerations informing recommendation
People at high risk of bowel cancer due to familial syndromes (eg Lynch syndrome and familial adenomatous polyposis) from a young age (eg 25 years) in discussion with a specialist	Commence daily low-dose aspirin	As clinically indicated	Conditional	National guideline³	This decision is likely to be on advice from or in consultation with specialist bowel cancer surveillance services
All people aged 50–70 years at average or higher risk of bowel cancer	Discuss and assess the option of daily low-dose (100 mg) aspirin	Opportunistically, as clinically indicated	Good practice point	National guideline³ Expert reviewer advice	Despite evidence of benefit after 10 years if taken for at least 2.5 years, aspirin is seldom used in practice unless there is a specific high-risk syndrome

Box 1. Assessing the risk of bowel cancer based on family history and no symptoms (excluding people with genetic predisposition)³
Category 1: Higher but less than twice the average risk	Only one first-degree^A relative diagnosed at age 60 years or older
Category 2: Risk two- to fourfold higher than average	Only one first-degree relative diagnosed before age 60 years One first-degree and one or more second-degree^B relatives diagnosed at any age Two first-degree relatives diagnosed at any age
Category 3: Risk at least fourfold and up to 20-fold higher than average	Two first-degree relatives AND one second-degree relative with colorectal cancer, with at least one diagnosed before age 50 years Two first-degree relatives AND two or more second-degree relatives with colorectal cancer diagnosed at any age Three or more first-degree relatives with colorectal cancer diagnosed at any age
^AA first-degree relative is an individual’s parent, sibling or child. A first-degree relative shares approximately half their genes with the individual.⁶ ^BA second-degree relative is an uncle, aunt, nephew, niece, grandparent, grandchild or sibling with one shared parent of the individual. A second-degree relative shares approximately one-quarter of their genes with the individual.⁷

Implementation tips

Use reminders and recall clinical software to prompt discussions about bowel cancer screening (eg to check knowledge of and participation in the screening program).
Offer the option of completing screening in the clinic setting, including storing and posting completed kits on behalf of community members.
Encourage the appointment of a bowel cancer screening ‘champion’ for promotion and use of home and in-clinic alternative-access iFOBT kits at all primary and community healthcare centres, with a focus on Aboriginal and Torres Strait Islander advocates and/or community members wherever possible.
Deliver culturally appropriate, place-based health promotion and community awareness raising activities to encourage participation in bowel cancer screening.
Provide staff training, including Aboriginal health workers and practitioners, nurses and GPs, regarding access to iFOBT kits for eligible people during an appointment, through the alternative-access NBCSP pathway. Aboriginal Community Controlled Health Organisations participating in the alternative-access-to-kits model can contact the National Aboriginal Community Controlled Health Organisation (NACCHO) for training options.
Healthcare providers can now bulk order and issue bowel screening kits to eligible patients for them to complete at home after a consult and a discussion regarding bowel cancer screening.
Make sure healthcare providers are aware of and are supported to register kits issued to community members into the NCSR. To ensure patients get their test results and that follow up is tracked, bowel screening kits issued to eligible people must be registered with the NCSR.
When possible, consider integrating practice software with the NCSR to seamlessly access and report clinical data on bowel screening, and to bulk order and issue NBCSP test kits.

Useful resources

Clinical guidelines

Accessing bowel cancer screening kits

NBCSP access to bowel screening kits
Australian Government and NCSR: NCSR quick start guide for the alternative-access-to-kits model

Notifying the NCSR

GP assessment report

General information and health promotion

Bowel cancer, also known as colorectal cancer, is cancer of the colon or rectum. It is the third most common type of cancer among Aboriginal and Torres Strait Islander people, and the second most common cause of cancer death.⁸ There is good evidence for primary preventive activities, such as healthy diet and physical activity, from a young age, in combination with early detection and removal of precancerous polyps through bowel cancer screening, and some evidence for consideration of chemoprevention (low-dose aspirin) from the age of 50 years.³

Although the incidence of bowel cancer is slightly lower for Aboriginal and Torres Strait Islander people compared with non-Indigenous Australians, survival rates are also lower and mortality rates are higher.⁹ Aboriginal and Torres Strait Islander men have a bowel cancer incidence rate approximately 1.4-fold higher than that among women, with overall highest incidence rates in those aged 65 years and over.¹⁰

The NBCSP in Australia is a publicly funded population-based screening program using iFOBT to detect pre-cancerous abnormalities and cancer in the bowel and, for those who participate in regular screening, can reduce the risk of deaths from bowel cancer by 15–25%.² The program was introduced in 2006 and underwent phased rollout in 2006–19.

In 2023, revised and updated guidelines on ‘Population screening’ for colorectal cancer and ‘Risk and screening based on family history’ were published in the Clinical practice guidelines for the prevention, early detection and management of colorectal cancer.^3,5 The recommended age to commence screening for people at average risk was changed to from 50 to 45 years.³Since July 2024, the updated NBCSP offers free iFOBT kits every two years for all eligible people aged 45-74 years.²

Aboriginal and Torres Strait Islander people have lower participation rates in the NBCSP compared with non-Indigenous Australians (31% versus 41%, respectively),¹¹ and there is a greater disparity in the uptake of screening in remote areas and areas of poorer healthcare access.^12,13

The need for effective and flexible models of access to and delivery of bowel screening resources for Aboriginal and Torres Strait Islander people has been documented.^4,10 Over a 12-month period from 2018 to 2019, the National Indigenous Bowel Screening Pilot evaluated whether providing bowel cancer screening kits through Aboriginal and Torres Strait Islander health services, rather than mailing them to individuals, increased rates of participation in screening and improved the equity of bowel cancer screening. In that study, participation in screening increased during the pilot period from 23% (usual pathway of individual mailed kits) to 39.8%.¹² Median days to return the iFOBT samples were also significantly reduced, and the program was assessed to be appropriate and cost-effective.¹³ The trial was so successful that in October 2022 it became standard practice under the NBCSP for healthcare providers to issue kits directly to community members as another way to participate in bowel cancer screening. NACCHO has been supporting member services to directly engage in bowel cancer screening in this way, and community-led health promotion and community awareness activities are contributing to increased screening participation.

Preventive activities

There is clear evidence the risk of bowel cancer is increased by tobacco smoking, alcohol, overweight and obesity, low physical activity and dietary factors such as low fibre and the consumption of red and processed meat.¹ These risk factors should be assessed and information and support offered to modify them, wherever practicable, in primary care settings. All adolescent and adult Aboriginal and Torres Strait Islander people should be offered culturally appropriate preventive advice and asked specifically about any family history of bowel cancer. This could be assessed, documented, discussed and updated at an annual health assessment and communicated through tailored health promotion and community awareness activities. Cultural safety is a key aspect of asking about family history among Aboriginal and Torres Strait Islander peoples given the impact of colonisation, racism, forced removal of children from families and communities and intergenerational trauma.

Primary preventive activities that can be discussed with all adults and inform community health promotion messaging include the following:^1,14

not smoking (tobacco is an established cause of up to 8% of bowel cancer)
eating a high-fibre diet
maintaining a healthy body weight and avoiding abdominal obesity
aiming for 30–60 minutes per day of at least moderate physical activity
limiting alcohol intake to a maximum of four standard drinks per day and not more than 10 standard drinks per week
limiting the consumption of red meat (especially when cooked until charred) and processed meats.

Refer to Chapter 2: Healthy living and health risks, Healthy eating, Physical activity and sedentary behaviour, Smoking and Alcohol and Chapter 15: Overweight and obesity.

Medication

Chemoprevention of bowel cancer for at least 2.5 years with low-dose (100–300 mg) daily aspirin for people aged 50–70 years with an average risk has been shown to reduce bowel cancer risk 10 years after the initiation of aspirin.⁵ The 2017 Australian guidelines recommend active consideration of aspirin in this group, particularly if there is added benefit of reducing cardiovascular and cerebrovascular events and thrombotic stroke. (A review of this was not included in the recently published guideline updates.) However, in clinical practice, aspirin is rarely used purely to prevent bowel cancer, except in the context of Lynch syndrome and familial adenomatous polyposis (J Keck, pers. comm., 2023), which is in line with Cancer Council Australia clinical practice guidelines for these high-risk conditions.² The choice to take aspirin can be considered and personalised based on age and sex and a holistic health lens, including the additional potential reduction in cardiovascular events, but also considering the risk of bleeding and renal impairment.^3,5

There is no current evidence for benefit over harms for the use of metformin, non-steroidal anti-inflammatory drugs (except aspirin), statins or bisphosphonates in the chemoprevention of bowel cancer at a population level.³

Screening

The NBCSP aims to reduce morbidity and mortality from bowel cancer by actively recruiting and screening all eligible people aged45–74 years with an iFOBT every two years, followed by colonoscopy for those with positive screening results.³ Screening is for people who do not have any signs or symptoms of bowel cancer. NBCSP screening activity, results and follow-up, including of colonoscopy, are recorded on the NCSR. The NCSR provides results and prompts for screening and follow-up to participants, so it is important for healthcare providers to notify the NCSR when NBCSP screening is initiated by the health service/practice or when NBCSP screening should be deferred if screening has occurred outside the program (see Useful resources).

Other bowel cancer screening tests are available, including flexible sigmoidoscopy and colonoscopy, computed tomography colonography and multitarget DNA stool testing,¹⁵ but considerations including cost, risks associated with invasive procedures, accessibility and resource allocation mean that these modalities are not part of the current population-based screening program.^3,16,17 Surveillance colonoscopy, rather than iFOBT screening, is recommended for high-risk individuals with known familial syndromes.⁵ It is important to clarify that patients with symptoms of macroscopic blood loss, change in bowel habits or a past history of bowel cancer should not participate in the screening program, but rather be referred directly for investigation and/or surveillance.^15,17 In addition, screening for bowel cancer with an iFOBT is inappropriate for high-risk individuals with chronic inflammatory bowel disease or certain genetic disorders, and in such cases specialist input is advisable.¹⁵

Assessing level of risk based on family history

People with a family history of bowel cancer may be at higher risk. The level of added risk depends on the number and closeness of relatives, and age at diagnosis.⁵ The level of added risk in an asymptomatic person is well described and informs guidelines for the age of starting, mode and interval of screening and/or surveillance³ (see Box 1).