He calculates that if half of those turning 60 had flexi-sig, each year 309 cancers and 102 deaths would be prevented.
By contrast, if 55 per cent of those aged 55 to 74 had poo-test screening, each year 30 cancers and 79 deaths would be prevented.
In both scenarios, around 5 per cent of those having the first test would proceed to colonoscopy, but far more colonoscopies would be needed with poo-test screening because of the much-larger number of people being tested.
Professor Cox cites the results of a 2010 study which found that, compared with no bowel screening, those who received flexi-sig had a 43 per cent lower risk of dying of bowel cancer and a 33 per cent lower future risk of developing bowel cancer.
"This is a much greater protection from bowel cancer than the proposed programme of the Ministry of Health," said Professor Cox.
"Countries such as the UK that developed bowel-screening programmes based on FOBT [faecal occult blood testing, a poo test] have been shifting to the more effective FS [flexi-sig] screening, and initial participation in FS screening has been 43.1 per cent," he wrote in the journal.
He told the Herald that an important advantage of flexi-sig, which could be done in general practice-related clinics by specially trained nurses, was the lower demand it placed on colonoscopy services.
The public health system's colonoscopy services are struggling to cope with existing demand despite increased funding.
The expected flood of extra patients from a national bowel cancer screening programme based on poo-testing is a key reason the introduction of such a scheme has been delayed, despite the positive results found overseas and in the pilot scheme at the Waitemata District Health Board.
It is likely that the national New Zealand scheme will at first have greater restrictions, such as a narrower age range, than the overseas trials and the Waitemata pilot, to avoid overwhelming colonoscopy services.
Other researchers have previously questioned the interpretation of flexi-sig studies by New Zealand researchers who support its introduction.
The patient support and lobby group Bowel Cancer New Zealand believes flexible sigmoidoscopy is a distraction from the pressing need for a national screening programme, which the Government has said it will start setting up early this year.
"We are so behind all other OECD countries in having a bowel screening programme, that the last thing we need to do is change direction now," said the group's chairwoman, Mary Bradley.
"There are some advocates for sigmoidoscopy compared to faecal occult blood testing in New Zealand and abroad; however, the balance of evidence, international opinion and cost-effectiveness still seem to favour the faecal immunochemical test.
"Bowel Cancer New Zealand also has concerns about the effectiveness of the sigmoidoscopy as it misses a significant proportion of cancers due to it not reaching around the entire colon.
"The ministry has taken extensive advice on this issue and we have no concerns about the quality of the advice received, just huge concerns that there is still no firm commitment or timeline in place from the Government on a national screening programme.
"We see no reason to back up the bus and start from scratch. The Government needs to get on with implementing a national screening programme now, as 1200 New Zealanders continue to die every year they delay."
The ministry said the clinical leader of its bowel screening team was unavailable so it could not comment until Monday.
FACT BOX
• A cancer researcher says New Zealand is on the wrong track with bowel cancer testing
• The Ministry of Health is investigating a national screening programme based on two-yearly poo-tests at home that are sent to a laboratory
• If hidden blood is found, the patient is offered colonoscopy
• Colonoscopy is an investigation of the whole large intestine with a flexible tube fitted with a camera and surgical instruments for taking tissue samples for testing
• Researcher Associate Professor Brian Cox says another kind of test would save more lives and be cheaper than a scheme based on poo-testing
• He recommends doing flexible sigmoidoscopy once, at age 60, and no poo test
• The flexible sigmoidoscopy tube goes only one-third the length of the large intestine, but this is where 60 per cent of colo-rectal tumours occur
• Some patients go on to have a colonoscopy as well
• A trial of flexible sigmoidoscopy found a 43 per cent reduction in the risk of dying of bowel cancer
• The ministry says poo-test screening for people aged 50 to 74 can lead to the avoidance of 36 per cent of bowel cancer deaths
