Every year more than 3000 New Zealanders are diagnosed with bowel cancer and 1200 die from the disease. That is 100 deaths a month from this pernicious disease, about the same as the number who die from breast and prostate cancer combined.

Bowel cancer is more common among those aged over 60, and occurs more among men than women.

For as yet unknown reasons, the country has among the highest rates of colorectal cancer in the world. Risk factors may include diets high in red meat and animal fats and low in fruit and vegetable fibre. Obesity and alcohol also appear to play a role.

New Zealand is slowly rolling out a national screening programme to test for the disease. The budget in May included funding of $38.5 million to support the implementation of the screening plan over the next three years. The programme starts this month in Wairarapa and Hutt Valley.

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It has been a gradual process up till now, as a successful trial has been run at Waitemata District Health Board for four years, where patients will join the national programme from the start of next year.

A recent study raises questions whether a condition of the national programme - that it will be freely available to eligible New Zealanders between the ages of 60 and 74 every two years - is adequate.

An analysis reported by the British Journal of Surgery found a decrease in the overall incidence of colorectal cancer in New Zealand, but an increased incidence of rectal cancer in those under 50 years of age. The study, which drew on the national cancer register, found bowel cancer increased for men under 50 by 18 per cent each decade between 1995 and 2012, and by 13 per cent for women of the same age.

According to the authors, the increasing incidence of rectal cancer among younger patients needs to be considered when implementing screening strategies. For the moment this seems unlikely, given the protracted implementation of the programme to this point, and the costs involved.

The Ministry of Health has had a world expert endorse the programme. Dr Linda Rabeneck, who chairs the World Endoscopy Organisation Colorectal Cancer Screening Committee, concluded it had been designed with great care and thought and targeted those in the highest risk group.

The Canadian specialist did note that the roll-out with the older age group provided the flexibility to expand the target population over time, as results from the programme were collected.

Despite this endorsement, an initiative in Christchurch will be keenly watched by those with a stake in the programme. A group of 12 Canterbury surgeons have agreed to do free clinics for younger patients with bleeding but who are unlikely to be seen by a public hospital. They will check symptoms in a quick procedure.

It is a notable step, and though the number of patients examined may be small, it could produce more evidence that the troubling emergence of bowel cancer among younger New Zealanders means the target screening age group needs reviewing.