Brian Cox: A cancer beater - and we're not using it

Cancer organisations need to promote the great gain in the reduction of bowel cancer that flexible sigmoidoscopy offers. Picture / 123RF

A 20-minute procedure called flexible sigmoidoscopy can reduce the subsequent risk of bowel cancer by 43 per cent. This is the biggest available reduction in bowel cancer risk for decades, if not ever. The reduction is much greater, and cheaper, than from eating more fresh fruit and vegetables each day for 20 or more years.

The 20-minute procedure involves passing a tube attached to a camera into the bowel. If important abnormalities are found, a biopsy can be taken and the tissue examined by a pathologist. If indicated, a more extensive similar examination of all the large bowel, a colonoscopy, is likely to be required.

This visual inspection enables adenomas, the precursors of bowel cancer, to be found and removed thus preventing them developing into bowel cancer.

The vast majority of adenomas do not bleed and are not detected by the faecal blood test being proposed for bowel screening in New Zealand. The effectiveness of flexible sigmoidoscopy for people 55-64 years of age was clearly established five years ago. So why has this information not been widely spread in New Zealand - a country with a very high bowel cancer incidence internationally?

Consumer groups and cancer organisations have been muted in their response to the breakthrough that flexible sigmoidoscopy provides. They appear to have been cajoled by promises from the Ministry of Health of an effective national bowel screening programme using two-yearly faecal testing. However, the current proposal is being restricted to 60-69 years of age with a promise of extension to the 60-74 age group should colonoscopy services be able to cope with the demand.

The amount of blood usually recommended to indicate the need for colonoscopy is 75-100 nanograms of haemoglobin per millilitre. However, to lower the number of people recommended for further investigation, the ministry is proposing to increase this to 200 nanograms. The ministry has estimated this will reduce the ability of bowel screening to detect bowel cancer, compared with the cut-off used in the Waitemata pilot study, by 17 per cent.

However, those in the 50-74 age group of the Waitemata health district who have already been invited to be screened will continue to have two-yearly screening. A major inequity, Waitemata and the rest of New Zealand, will be introduced. Waitemata has lower than average bowel cancer incidence than the country overall, and the southern South Island in particular, so the pilot study results provide a lower than average bowel cancer detection rate regardless of the method of screening used.

However, the rate of detection of bowel cancer by flexible sigmoidoscopy at age 55 to 64 is much higher than that of the proposed faecal blood testing programme. The Waitemata pilot has shown that bowel screening as originally envisaged cannot be introduced in New Zealand.

The cut-off and age ranges for many existing bowel screening programmes are being altered around the world because their colonoscopy services are not coping with the workload that faecal blood test screening produces.

In Scotland and England the cut-off values of their existing programmes have had to be raised because the colonoscopy services are failing to meet the needs of their programmes.This tightening of the age groups to which it is offered is recognised as not being best practice but is symptomatic internationally of the faecal test screening approach. No change in the flexible sigmoidoscopy component of the UK screening programme has been considered necessary.

The current approach of the Ministry of Health is to copy what Ireland is introducing, a country without a robust history of cancer screening. Why the ministry and its advisers wish to unnecessarily inflict the major problems of other countries on the New Zealand public is unfathomable. Having got it so wrong it appears difficult for those involved to admit the error of continuing to pursue faecal test screening alone.

Unlike other countries we have a great opportunity to avoid the pitfalls of their screening programmes by introducing flexible sigmoidoscopy screening. This places a much lower demand on colonoscopy services.

The way the Ministry of Health is suggesting bowel screening is implemented prevents any accurate assessment of its impact on future bowel cancer mortality or incidence. For more than 20 years there has been a way to introduce cancer screening that provides very precise measures of its effect on cancer incidence and mortality. This approach has been used extensively in Finland. No significant reduction in bowel cancer mortality from the faecal blood testing programme in Finland over the past eight years has been found.

The Treasury was correct, earlier this year, to put a red flag on the current approach to bowel screening in New Zealand. The current overseas experience strongly suggests that the Ministry's plan is fraught with risks of excess cost, failure in delivery, and an inability to measure any beneficial, or possibly harmful, effects.

In contrast, the cost-effectiveness of flexible sigmoidoscopy screening has been reviewed by the International Agency for Research on Cancer and it was found that flexible sigmoidoscopy screening may be cost-saving due to the bowel cancers prevented.

Cancer organisations were promised a timely bowel screening programme covering the 50-74 age group with two-yearly faecal testing. The pilot study has shown this not to be possible. The demand on colonoscopy services from the more inferior programme for those 60-69 years of age is likely to severely inhibit extension of the programme.

Cancer organisations need to promote the great gain in the reduction of bowel cancer that flexible sigmoidoscopy offers.

Associate Professor Brian Cox, a specialist in public health at the Otago University school of medicine, is a world expert on cancer screening.