There’s an alarming rise in colorectal cancer rates in younger New Zealanders and especially Māori, according to a new study from the University of Otago.
The study is the most up-to-date, population-based data yet presented to describe overall trends in colorectal cancer rates (CRC) incidence in Aotearoa New Zealand by age, sex, and site of disease, between 2000 and 2020.
It shows colorectal cancer rates in older age groups have decreased but rates of early onset colorectal cancer have risen by 26% per decade on average over the past 20 years.
Out of the total of 56,761 cases of CRC diagnosed in New Zealand during this time, 3702 of these were early onset, according to the research.
Incidence of early onset increased by 26% per decade on average during that time period with 44% occurring in the 45 to 49 age group, compared with an 18% decrease per decade in those aged 50-79.
The study data modelling predicted that if these trends continued to 2040, there would be 524 cases of early onset colorectal cancer diagnosed per year in Aotearoa New Zealand, an increase of 255 cases per year when compared with numbers seen in 2020.
Māori rates ‘increasing disproportionately’
Lead author Dr Oliver Waddell, from the department of surgery at the university, said the results showed CRC rates in Māori are increasing disproportionately in comparison to the overall population, driven by increasing numbers of younger Māori patients.
While overall incidence of CRC remained lower in Māori compared to the total population, incidence rates of colorectal cancer in Māori under 50 years rose by 36% per decade on average, faster than the rates seen in the total population, which was 26%.
Māori were also disproportionately affected by EOCRC, with 18% of all cases diagnosed in Māori in 2020 being under the age of 50 years, compared to 8.5% in the overall population.
“This is of grave concern because, once they are diagnosed with colorectal cancer, Māori are more likely to die from their disease than non-Māori, and also more likely to be diagnosed with stage 4 advanced disease, possibly due to delayed diagnosis and inequitable access to cancer treatment,” said Waddell.
“If these increases go on unchecked, we will see colorectal cancer rates in Māori overtake those of the general population.”
Call for younger screening age
On the back of these findings, the study authors were now calling for the bowel cancer screening age in Aotearoa New Zealand, which was currently 60 for non-Māori and 50 for Māori, to be extended and lowered further, to help combat inequity.
“We believe screening for average-risk people in New Zealand should start at least age 45,” said Waddell.
“Unfortunately, in over a third of patients diagnosed with a bowel cancer under the age of 50, by the time symptoms have developed, the cancer has already spread to stage 4 disease, so we need to find these cancers earlier before it’s too late for a cure.”
The study reports that Canada, UK, and Germany screen their general population from age 50, while the USA and Australia recently decided to screen from age 45, with several American guidelines now recommending screening from age 45 for all.
“Increasing our endoscopy capacity should be a priority to allow us to match these other countries because, in the long term, it will save the New Zealand health system money from reduced treatment costs due to earlier diagnosis, not to mention the lives that will be saved.”
Reasons behind increase not yet known
The authors added more research was needed to establish why rates were rising so dramatically both here and overseas.
While conventional risk factors for bowel cancer were known such as obesity, alcohol, processed meat, sugary drinks and a high-fat, low-fibre diet, they added the microbiome in EOCRC patients differs – possibly reflecting the impact of early life events and/or environmental factors such a caesarean delivery, formula feeding, antibiotic use, changing diet, synthetic food dyes, MSG high fructose corn syrup, or microplastics.
The authors emphasised that, despite the rising incidence of early onset, CRC remained largely a disease of older adults. New Zealand has one of the highest rates of bowel cancer in the world, with more than 3000 diagnosed annually, second only to prostate and breast cancers. It remained the second highest cause of cancer death with more than 1200 people dying each year as a result.
Waddell said the increasing impact of our ageing population was also likely to become a huge factor in coming years and a major challenge for our already struggling health system. The number of people aged over 80 was set to double by 2040, with bowel cancer rates in this age group predicted to increase from 800 to over 1800 during that time.
Alana Ewe-Snow Director of Prevention at Health NZ/Te Whatu Ora issued a statement today.
“Health NZ/Te Whatu Ora always welcomes new research that leads to better health outcomes for New Zealanders.
“We are currently working with partner agencies to provide advice on the age extension for bowel screening programme across the country.”