The National Bowel Screening Programme is only open to people aged 60 to 74, whereas most countries start screening at 50. File photo Photo: RNZ
A dramatic rise in colorectal cancers in people under 50 is prompting calls for earlier screening for the disease.
New Zealand has one of the highest rates of bowel cancer in the world, with 3000 people diagnosed a year.
It kills more than 1200 New Zealanders each year and is the second highest cause of cancer death after lung cancer.
But the National Bowel Screening Programme is only open to people aged 60 to 74, whereas most countries start screening at 50.
Writing in the New Zealand Medical Journal on Friday, a group of doctors and researchers argued screening should start at 45 for the general population and 40 for Māori and Pasifika.
Lead author Oliver Waddell said screening earlier would save lives and money.
"Eight major insurance companies in the United States are now funding screening down to 45 in their private patients, due to it being cheaper to screen those patients rather than wait another three of four years for a cancer to declare itself down the track as a more advanced cancer, which is much more expensive to treat," Dr Waddell said.
"That's aside from the human impact."
Overall, rates of bowel cancer are decreasing - possibly due to older people having precancerous polyps investigated.
However, cancers in those under 50 continue to increase dramatically.
The report notes that from 1995 to 2012, colon cancer in New Zealand men younger than 50 increased by 14 percent, and the incidence of rectal cancer increased by 18 percent in men and 13 percent in women.
For Māori, 30 percent of bowel cancer in women and 24 percent of cases in men happen before the age of 50.
Unpublished data over 25 years to 2020 found 45 percent of all early onset colorectal cancers were in 45 to 49 year olds, meaning almost half could be prevented or diagnosed if screening was lowered to 45 and even more reduced if started at 40.
"In the United States, the incidence of early-onset bowel cancer has doubled since the 1990s, and by 2030, it has been estimated that more than one in 10 colon cancers and nearly one in four rectal cancers will occur in people aged under 50," Waddell said.
The reasons for this increase were not yet known, he said.
It was unlikely to be hereditary, because most patients with early onset bowel cancer did not have a family history of the disease.
"It's likely to be something to do with the environment interacting with the bacteria in our gut, and how that's interacting with the bowel," Waddell said.
"So things like changing diet, changing antibiotic usage, they could all be playing a role, as well as things like obesity, alcohol, smoking - they're all potentially implicated.
"But as yet, we don't have a clear cause of what's driving it."
Co-author professor Frank Frizelle, who is also medical advisor to Bowel Cancer New Zealand, said many young people with the deadly disease were being diagnosed too late because of a lack of access to screening.
He regularly carries out colonoscopies at Christchurch's Charity Hospital on patients with symptoms who have been turned down in the public system.
"And [on] almost every list, I will find someone with a precancerous lesion. And that's only in people under 50."
