September 13, 2022

Bowel Cancer New Zealand Position Statement: Early-onset bowel cancer

Bowel cancer in young people is increasing in New Zealand, and greater awareness about the significance of its symptoms in this group is urgently needed.

Key messages:

  • Early-onset bowel cancer refers to people diagnosed before age 50
  • The incidence of early-onset bowel cancer is increasing
  • Early-onset bowel cancer has different risk factors and clinical behaviour than late-onset bowel cancer
  • There is a need for education to raise awareness about early-onset bowel cancer in young adults and primary care health professionals to promote early diagnosis and optimal treatment
  • Young people with symptoms, e.g. bleeding from the bowel, a change in bowel habit (either frequency or constancy), cluster bowel motions and/or feeling like their bowel cannot be emptied, should report them to their general practitioner, especially if they are persistent.
  • There should be a lower threshold for colonoscopy or flexible sigmoidoscopy in young patients with persistent symptoms
  • The age of eligibility for bowel cancer screening should be lowered to 45 years

Early-onset bowel cancer in New Zealand

The rate of bowel cancer in people aged under 50 in New Zealand is increasing. This is part of a worldwide trend that is occurring despite the overall rate of bowel cancer decreasing in many countries.1,2 From 1995 to 2012, colon cancer in New Zealand men aged under 50 increased by 14% and the incidence of rectal cancer increased by 18% in men and 13% in women aged under 50.3 This finding has been repeated and is consistent with other studies from Australia, the United States, Canada, the United Kingdom, France and Asia that consistently show a rapid increase in early-onset bowel cancer.1,4–8 In the United States, the incidence of early-onset bowel cancer has doubled since the 1990s and by 2030 more than 1 in 10 colon cancers and nearly 1 in 4 rectal cancers will occur in people aged under 50.4,5,9

Early-onset bowel cancer is different in many ways to late-onset bowel cancer. There is a different distribution within the colon, with early-onset cancer often occurring in the distal bowel involving the rectum, rectosigmoid and sigmoid colon. Patients with early-onset bowel cancer also tend to present with more advanced disease, have a more aggressive histopathology with more poorly differentiated cancer, and are more likely to have lymphatic and neural involvement.2,5,10 Despite this, stage for stage they tend to have a better prognosis.

Why is it increasing?

The exact reasons why bowel cancer is increasing in young people are not known. As expected, there are more cancers with an inherited genetic abnormality (germline mutation) in patients with early-onset bowel cancer because people with germline mutations can develop cancer at a younger age. However, it is the cancers with no germline mutations (sporadic) that are increasing at a rapid rate in those aged under 50, the cause of which is as yet unknown.

With late-onset bowel cancer, a number of lifestyle risk factors are known including a lack of physical exercise, alcohol consumption, smoking, and a Western diet with reduced intake of fruit and vegetables and a high intake of red meat and fast food.1,4 All these factors contribute to obesity which is also a substantial risk factor for bowel cancer.1 The evidence of these factors being drivers in early-onset bowel cancer is much less certain.

The gut microbiome is likely to be involved in the development of sporadic bowel cancer and it is also likely to contribute to the risk of early-onset bowel cancer. The gut microbiome is influenced by a range of environmental factors including our exposures in early infancy, diet, and antibiotic use, all of which have changed over the same period that early-onset bowel cancer has increased.2,5 Colonisation by bacteria that produce certain toxins, e.g. Bacteroides fragilis, have been shown to cause changes to the gut mucosa that increase the risk of bowel cancer.1 Research has recently shown different patterns of bacteria in the microbiome of patients with early-onset bowel cancer compared to those diagnosed at a later age or healthy controls.11

Increased awareness is needed

Unfortunately, many younger patients present with advanced stage disease and a cure is not possible. There needs to be an increased awareness about the significance of bowel cancer symptoms by the public, primary care health professionals and those accepting referrals for specialist appointments. Delays to diagnosis often occur due to younger patients not seeking help when symptoms arise and when health professionals do not adequately investigate symptoms in younger people because they believe they are ‘too young’ to have symptoms caused by bowel cancer.12

Younger patients are more likely to have an alternative explanation for symptoms, e.g. haemorrhoids, anal fissures, inflammatory bowel conditions or dietary intolerance.13,14 This is especially so with the intermittent nature of initial symptoms. Concerning intermittent symptoms should not be discounted, however, as they may develop into a constant pattern and become persistent.13 The threshold for colonoscopy in symptomatic younger patients needs to be lowered in New Zealand.3 Given that early-onset bowel cancer frequently occurs as a left-side tumour that is easier to detect on colonoscopy, a lower threshold for investigation would provide earlier diagnoses of early-onset bowel cancer.10

N.B. Bowel Cancer New Zealand has created a “Never Too Young” brochure to help health professionals diagnose bowel cancer.

The age for screening must be lowered

Currently, the National Bowel Screening Programme is only open to people aged 60-74, whereas most countries with programmes begin screening for bowel cancer at age 50.2 The American Cancer Society recommends that screening should begin at age 45.15 The age of eligibility for screening in New Zealand should also be lowered to 45 given that this country has some of the highest rates of bowel cancer in the world and that the rates of bowel cancer in people aged under 50 are continuing to rise. This is particularly important for Māori as 30% of bowel cancer in Māori females and 25% in Māori males occurs before age 50.16

Tailoring care for younger patients

People diagnosed with bowel cancer at a young age may have different needs such as family planning, childcare, meals, transport, and access to psychologists and physiotherapists. Bowel Cancer NZ advocates for tailored care and increased support and resources for young people diagnosed with bowel cancer and their whanau.

Act early to reduce risk

Early-onset bowel cancer can occur in fit and healthy people and we do not know how to prevent it. Crucially, talk to your doctor if you develop symptoms including a change in bowel habit, feeling like your bowels will not empty properly, unexplained weight loss, or tiredness. Finally, join Bowel Cancer NZ in advocating for the age of screening in Aotearoa New Zealand to be lowered to 45 years so that bowel cancer can be detected early and cured.

This position statement was created independently by Bowel Cancer New Zealand and was not funded or supported by any external organisations.


1. Chittleborough TJ, Gutlic I, Pearson JF, et al. Increasing Incidence of Young-Onset Colorectal Carcinoma A 3-Country Population Analysis. Dis Colon Rectum. 2020;63(7):903-910. doi:10.1097/DCR.0000000000001631

2. REACCT Collaborative, Zaborowski AM, Abdile A, et al. Characteristics of Early-Onset vs Late-Onset Colorectal Cancer: A Review. JAMA Surg. 2021;156(9):865-874. doi:10.1001/jamasurg.2021.2380

3. Gandhi J, Davidson C, Hall C, et al. Population-based study demonstrating an increase in colorectal cancer in young patients. Br J Surg. 2017;104(8):1063-1068. doi:10.1002/bjs.10518

4. Bailey CE, Hu CY, You YN, et al. Increasing disparities in the age-related incidences of colon and rectal cancers in the United States, 1975-2010. JAMA Surg. 2015;150(1):17-22. doi:10.1001/jamasurg.2014.1756

5. Stoffel EM, Murphy CC. Epidemiology and Mechanisms of the Increasing Incidence of Colon and Rectal Cancers in Young Adults. Gastroenterology. 2020;158(2):341-353. doi:10.1053/j.gastro.2019.07.055

6. Patel P, De P. Trends in colorectal cancer incidence and related lifestyle risk factors in 15-49-year-olds in Canada, 1969-2010. Cancer Epidemiol. 2016;42:90-100. doi:10.1016/j.canep.2016.03.009

7. Young JP, Win AK, Rosty C, et al. Rising incidence of early-onset colorectal cancer in Australia over two decades: report and review. J Gastroenterol Hepatol. 2015;30(1):6-13. doi:10.1111/jgh.12792

8. Chauvenet M, Cottet V, Lepage C, et al. Trends in colorectal cancer incidence: a period and birth-cohort analysis in a well-defined French population. BMC Cancer. 2011;11:282. doi:10.1186/1471-2407-11-282

9. Siegel RL, et al. Colorectal cancer statistics, 2017. CA Cancer J Clin. 2017;67(3):177-193. doi:10.3322/caac.21395

10. Baran B, Mert Ozupek N, Yerli Tetik N, et al. Difference Between Left-Sided and Right-Sided Colorectal Cancer: A Focused Review of Literature. Gastroenterology Res. 2018;11(4):264-273. doi:10.14740/gr1062w

11. Kong C, Liang L, Liu G, et al. Integrated metagenomic and metabolomic analysis reveals distinct gut-microbiome-derived phenotypes in early-onset colorectal cancer. Gut. Published online August 11, 2022:gutjnl-2022-327156. doi:10.1136/gutjnl-2022-327156

12. Blackmore T, Chepulis L, Rawiri K, et al. Patient-reported diagnostic intervals to colorectal cancer diagnosis in the Midland region of New Zealand: a prospective cohort study. Fam Pract. 2022;39(4):639-647. doi:10.1093/fampra/cmab155

13. bpacnz. Referral of patients with features suggestive of bowel cancer: Ministry of Health guidance. Published online 2020.

14. Bowel Cancer New Zealand. Never to young.

15. Wolf AMD, Fontham ETH, Church TR, et al. Colorectal cancer screening for average-risk adults: 2018 guideline update from the American Cancer Society. CA Cancer J Clin. 2018;68(4):250-281. doi:10.3322/caac.21457

16. McLeod M, Harris R, Paine SJ, et al. Bowel cancer screening age range for Māori: what is all the fuss about? N Z Med J. 2021;134(1535):71-77.