Editorial: Bowel cancer trial's value needs proving

The bowel is this country's most common source of cancer. Photo / Getty Images

Some parts of the body give no sign of a cancer until it is too late to remove it. Other organs give ample warnings. The bowel is one of the latter. In fact, no other organ delivers evidence of its condition quite as obviously and regularly, if all is well. So why do 30 per cent of cases in New Zealand go undetected until they have to be treated in hospital? And with 24 per cent so advanced the cancer has spread to other organs?

These findings of a three-year study go some way to explaining why the bowel is this country's most common source of cancer, and its second-highest cause of death from cancer. Bowel Cancer New Zealand is quick to cite the findings as reason to introduce a national screening programme that would cost at most $60 million a year.

The Government is wary. It introduced a pilot screening programme in the Waitemata District Health Board area four years ago. People aged 50-74 were sent self-sampling kits and invited to send their sample for testing. A year or two on, a second invitation was sent to those who had not responded. The pilot had been scheduled to finish in December this year but it has been given a two-year extension.

Clearly it is not going as well as expected. It may be just the yuk factor that is limiting its uptake, but that is a factor the trial programme has to overcome if it is to prove national screening would be worthwhile. People alert to their bodily functions and comfortable discussing them with their doctor probably do not need a screening programme. It is the careless and squeamish the programme needs to convince. If it can reach those whose cancer would not otherwise be detected early, screening could be good value for taxpayers. An outlay of $60 million could be recovered in savings on attempts to contain the cancer in its advanced stages.

But no screening programme is perfectly reliable. All suffer to some extent from inaccurate results. Tests that return with a false negative can leave patients without treatment they need, and those that record a false positive cause people anxiety and put them through needless procedures that are painful and debilitating.

Even accurate results do not say whether an early-stage cancer will progress to be fatal. Screening of other cancers leads to detection and treatment of many more cases annually than the number who died of the cancer in a typical year before screening began. That is not a reason to reject screening, but it ought to be kept in mind.

Modern diagnostic techniques are one of the reasons healthcare expenses are rising so fast in developed countries. It is not just the equipment and technicians required for procedures such as colonoscopy, it is the increased workload they generate. Practitioners and patients become persuasive advocates for ever more public spending for more benefit. And that can often be a good thing. Governments face easy criticism when they keep a cautious hand on the purse - but they are usually right to do so. Screening for any cancer is a big decision and the case needs to be compelling. Only when it is should a national programme proceed.