Bowel screening

Bowel cancer is cancer in any part of the large bowel, which includes the colon and rectum. It is also known as colorectal cancer. These terms may be used interchangeably in our work, depending on the context and audience.

Aotearoa New Zealand (NZ) has one of the highest bowel cancer age-standardised incidence rates in the world (1). It is currently the second most commonly diagnosed cancer and the second leading cause of cancer-related deaths (2). NZ has high rates of delayed diagnosis of bowel cancer, leading to poorer cancer outcomes, particularly for Māori and Pacific peoples (3).

Bowel cancer incidence rates are decreasing in the older population but increasing in people aged under 50. However, bowel cancer is still far more common in people over the age of 50 (1). The factors causing the increase in early onset bowel cancer are not clear and very little is known about the natural history of bowel cancer in younger adults.

Bowel cancer survival depends on the stage of the disease, ranging from 90% 5-year net survival for early-stage bowel cancer, to 14% for late-stage disease (4).

Population-based bowel cancer screening is an effective way to reduce both incidence and death from bowel cancer. Screening can identify bowel cancer at an early stage, when treatment is more likely to be successful (5,6). It can also prevent bowel cancer because it almost always arises from benign polyps (growths), and these can be removed when detected by colonoscopy.

The National Bowel Screening Programme (NBSP) currently invites New Zealanders aged 60-74 to have a free bowel screening test every 2 years. The Government recently announced the age will be lowered to 58, starting in two regions from October 2025 (7).

The success of the NBSP relies on high, sustained and equitable participation.

The participation rate for NZ European/other is 62%, exceeding the target participation rate of 60%, but the programme's reach is much lower to Māori (50.2%) and Pacific (38.7%) and Asian peoples (43.7%) (8).

As screening has enormous potential to save lives, increasing the programme’s reach (to increase informed participation) among under screened groups should be prioritised.

There is also a need to explore the effectiveness and feasibility of lowering the NBSP starting age still further for Māori and Pacific peoples. These peoples have a younger age structure, lower life expectancy and a higher proportion of bowel cancer occurring below current screening eligibility (9,10). This means these groups have less opportunity to benefit from the programme currently.

There is uncertainty regarding the benefit of population bowel screening in younger adults. No controlled studies have specifically assessed incidence, mortality, or the risks and costs of screening people under age 50 (11,12). There is also uncertainty about how the FIT test performs in this age group and an incomplete understanding of the natural history of disease in younger people (13). Therefore, the Cancer Society’s position is that current evidence does not support a recommendation for population bowel screening for individuals younger than 50 years.

As well as this, the scarcity of clinical resources in NZ needs to be considered. Positive FIT tests need confirmation diagnostic colonoscopy. The increased demand on colonoscopy services among people below 50 could crowd out those with a greater likelihood of benefit (e.g. people with symptoms, people over 50) whose access to colonoscopy is often delayed given limited capacity.

Globally, few comparable countries currently offer population bowel screening below 50. In 2024, Australia lowered its screening age to 45 years. However, this was based on predictive modelling studies, and on a range of untested assumptions (14).

• New Zealanders should consider completing a bowel screening test every two years when they are invited to take part in the National Bowel Screening Programme.
• The decision to be screened above 75 years should be made on a whānau or individual basis, with support from a health provider.
• People who have bowel symptoms and have had a negative result on a screening test may still require further tests and should discuss their symptoms with their health provider.
• Anyone with symptoms of bowel cancer (at any age) or have questions or concerns about their risk of bowel cancer should see their health provider and not wait for a screening test to be sent to them. 
• People at higher risk for bowel cancer due to a personal or strong family history of bowel cancer or adenomatous polyps or inflammatory bowel disease should talk to their health provider as tests and investigations from an earlier age may be needed.
• The Cancer Society does not recommend or endorse bowel screening test kits outside of the NBSP. A positive result from a NBSP test kit is followed by a free follow up test (usually a colonoscopy within a certain time frame). This is not available for test kits purchased and used outside of the programme.

• The recommended strategy for population bowel screening in NZ for those at average risk of bowel cancer and without symptoms, is FIT testing every 2 years, starting at 50 years and continuing to 74 years.
• Accelerate the provision of bowel screening to Māori and Pacific peoples from age 50.
• Ensure the implementation of targeted, proven strategies to reduce inequities in screening participation, including community engagement, tailoring outreach to specific populations and awareness campaigns.
• Enhance awareness of bowel cancer red flag symptoms, family history, and genetic syndromes among clinicians and the community to speed evaluation and diagnosis of younger patients. 
• Identify and address factors that inhibit the pathway to early diagnosis and treatment, such as appropriate investigation and referral of younger adults, lengthy diagnostic delays, limited availability of diagnostic services, health workforce shortages and difficulty in accessing specialists.
• Accelerate the change in pathway to allow FIT tests for people with symptoms to improve case detection and enable more efficient use of colonoscopy services.

• Support NZ research investigating topics such as the feasibility and efficacy of lowering the NBSP start age further for Māori and Pacific peoples and alternative approaches to population screening among younger adults such as personalised risk assessment screening approaches.

1. IARC. Global Cancer Observatory [Internet]. 2025 [cited 2025 Mar 28]. Available from: https://gco.iarc.who.int/en
2. Health NZ. Cancer web tool [Internet]. 2025 [cited 2025 Mar 28]. Available from: https://www.tewhatuora.govt.nz/for-health-professionals/data-and-statistics/cancer/data-web-tool
3. Sharples KJ, Firth MJ, Hinder VA, Hill AG, Jeffery M, Sarfati D, et al. The New Zealand PIPER Project: colorectal cancer survival according to rurality, ethnicity and socioeconomic deprivation-results from a retrospective cohort study. New Zealand Medical Journal. 2018;131(1476):24–39.
4. Siegel RL, Wagle NS, Cercek A, Smith RA, Jemal A. Colorectal cancer statistics, 2023. CA Cancer J Clin. 2023 May;73(3):233–54.
5. Hewitson P, Glasziou P, Irwig L, Towler B, Watson E. Screening for colorectal cancer using the faecal occult blood test, Hemoccult. Cochrane Database Syst Rev [Internet]. 2007 [cited 2025 Mar 31];2007(1). Available from: https://pubmed.ncbi.nlm.nih.gov/17253456/
6. Heresbach D, Manfredi S, D’Halluin PN, Bretagne JF, Branger B. Review in depth and meta-analysis of controlled trials on colorectal cancer screening by faecal occult blood test. Eur J Gastroenterol Hepatol [Internet]. 2006 Apr [cited 2025 Mar 31];18(4):427–33. Available from: https://pubmed.ncbi.nlm.nih.gov/16538116/
7. Health NZ. Lowering the bowel screening starting age to 58 At a Glance [Internet]. 2025 [cited 2025 Mar 31]. Available from: https://www.tewhatuora.govt.nz/assets/Health-services-and-programmes/Bowel-screening/At-a-glance-Lowering-the-bowel-screening-starting-age-to-58.pdf
8. Health NZ. National Bowel Screening Programme [Internet]. 2025 [cited 2025 Mar 31]. Available from: https://tewhatuora.shinyapps.io/nphs-nbsp/
9. McLeod M, Harris R, Paine SJ, Crengle S, Cormack D, Scott N, et al. Bowel cancer screening age range for Māori: what is all the fuss about? N Z Med J [Internet]. 2021 [cited 2025 Mar 31];134(1535). Available from: https://nzmj.org.nz/journal/vol-134-no-1535/bowel-cancer-screening-age-range-for-maori-what-is-all-the-fuss-about
10. Waddell O, Pearson J, McCombie A, Marshall H, Purcell R, Keenan J, et al. The incidence of early onset colorectal cancer in Aotearoa New Zealand: 2000–2020. BMC Cancer [Internet]. 2024 Dec 1 [cited 2025 Mar 31];24(1):1–10. Available from: https://bmccancer.biomedcentral.com/articles/10.1186/s12885-024-12122-y
11. Davidson KW, Barry MJ, Mangione CM, Cabana M, Caughey AB, Davis EM, et al. Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement. JAMA - Journal of the American Medical Association. 2021 May 18;325(19):1965–77.
12. Qaseem A, Harrod CS, Crandall CJ, Wilt TJ, Balk EM, Cooney TG, et al. Screening for Colorectal Cancer in Asymptomatic Average-Risk Adults: A Guidance Statement From the American College of Physicians (Version 2). Ann Intern Med [Internet]. 2023 Aug 1 [cited 2025 Mar 31];176(8):1092–100. Available from: https://pubmed.ncbi.nlm.nih.gov/37523709/
13. Yeh JH, Tseng CH, Wang WL, Chen CI, Liu YP, Lee YC, et al. Performance of the Fecal Immunochemical Test in Detecting Advanced Colorectal Neoplasms and Colorectal Cancers in People Aged 40-49 Years: A Systematic Review and Meta-Analysis. Cancers (Basel) [Internet]. 2023 Jun 1 [cited 2025 Mar 31];15(11). Available from: https://pubmed.ncbi.nlm.nih.gov/37296969/
14. Cancer Council Australia. Clinical practice guidelines for the prevention, early detection, and management of colorectal cancer: Population screening [Internet]. 2023 [cited 2025 Mar 31]. Available from: Clinical practice guidelines for the prevention, early detection, and management of colorectal cancer: Population screening