Programme a 'poor gamble'

The Hutt Valley and Wairarapa District Health Boards  began the National  Bowel Screening Programme last month, and Southern will follow next year.

Former ODT health reporter Elspeth McLean looks at some of the issues concerning the programme and asks whether the hype  surrounding  the roll-out will match the reality.

If only bowels were sexy. Maybe if they could be seen and not just heard; if we could squash them into a push-up bra and ogle them, we would care more about the adequacy of the proposed National Bowel Screening Programme.

Politicians of every hue might be falling over each other in an election year to tell us that what is planned is not good enough. They might be demanding that, because of the limitations of what is proposed, information provided to participants must be top notch, so no-one is given a false sense of security. They might be insisting on a clear plan for improvements to the programme, a plan for a programme with an emphasis on preventing cancer rather than finding it.

If they are saying any of this, they are doing so quietly.

Clinical director of the programme Associate Prof Susan Parry tells us that when the programme is fully operating, more than 700,000 people will be invited for free screening every two years, and initially between 500 and 700 cancers are expected to be found annually.

This programme should be exciting in a country where we have more than 3000 new cases recorded every year and one of the highest death rates from colorectal cancer in the developed world - about 1200 deaths a year.

But what Prof Parry is reluctant to highlight is that the national programme is the poor relation compared with the pilot.

Only 62% of the people found with cancers in the pilot programme in Waitemata would have had them detected if the pilot programme had used the age range and blood/faeces test level of the national programme.

This percentage, released to me after months of obfuscation in answers to questions and also tucked away near the bottom of a media release from Prof Parry, which received little coverage, is as close as the screening programme comes to indicating the impact of the difference between the national programme and the pilot.

To March this year, 375 pilot participants had been diagnosed with cancer, but if the age range and test threshold for the national programme had been used, about 142 of those people would not have had cancer detected.

The screening programme says ''it is important to note that it would be overly simplistic to try to apply this figure beyond the first screening round of the National Bowel Screening Programme, as the threshold in the first screening round influences the number of cancers found in the second screening round. For example, cancers not detected in the first screening round may then be detected in the second screening round - lifting the overall detection rate''.

The less sensitive threshold chosen for the national programme's blood/faeces test, which could indicate bowel cancer may be present, will mean many cancers will remain either unfound or not found early enough to be cured. The likelihood of pre-cancerous growths being found will also be lower in the national programme.

No screening programme guarantees to pick up all disease. There are always false positive tests and false negative tests. In the case of bowel screening, using the faecal immunochemical test (FIT) as the initial test, blood detected in faeces might be unrelated to a cancer.

If a cancer or adenoma (a growth which may be a pre-cursor to cancer) is not bleeding or not doing so at the time the test is taken, or not bleeding enough to meet the programme's blood /buffer threshold, it will not trigger further investigation.

This is illustrated in the results of the pilot programme. Twenty-seven people who had returned negative tests in the first round of the pilot were found to have cancer in the second round - this figure included nine people with stage 3 cancers (where the cancer had extended beyond the bowel wall to nearby lymph nodes but not other parts of the body) and one stage 4 (where the cancer had gone beyond the bowel to other parts).

To date, the national screening programme has refused to release the number of interval cancers in the pilot programme - those cancers diagnosed between the rounds of the programme in people who have had either a negative screening result or a positive result and nothing revealed in the subsequent colonoscopy. It says information has been gathered on these but not analysed.

New Zealand screening authority Associate Prof Brian Cox, of the University of Otago, said the interval cancers should have been published in the report of the pilot as this was ''vital information about performance, but I am not sure they understood that''.

What was known was that with the higher cut-off test threshold level for the national programme, there would be ''13% of the total detected added as interval cancers'', which Prof Cox said would make the sensitivity of the screening test poor.

Sensitivity is the ability of a test to correctly identify those with disease. A highly sensitive test rarely gives a false negative result.

The Sapere Research Group, which completed its ''final'' evaluation report on the first two rounds of the pilot before all the data was in, used international data and some information from the pilot to estimate the sensitivity of the screening test at different FIT cut-offs. At the national programme cut-off of 200ng haemoglobin/ml buffer, it estimated the sensitivity of a single FIT to be 70.6% for stage 3 or 4 cancer (compared with 85.9% at the pilot threshold) and 50.4% for stage 1 or 2 cancer (59.7% in the pilot). The estimated ability of the new threshold to correctly find those with adenomas smaller than 10 millimetres was almost half that estimated for the pilot - 3.7% compared with 7.7%. Larger adenomas will also be less likely to be found at an estimated 17.4% compared with 25.2%.

Prof Parry has been emphasising the age range for the national programme, which will be 60 to 74 (the pilot was 50 to 74), has been chosen because most cancers in the pilot were found in the higher age range.

Similarly, she points out that 86% of colonoscopies performed on pilot participants who had a blood/buffer reading between the pilot 75ng Hb/ml buffer threshold and the new much less sensitive level of 200ng Hb/ml buffer to be used in the national programme did not find a cancer or advanced adenoma. (A colonoscopy examines the whole of the bowel and allows for the removal of adenomas, sometimes called polyps.)

More than 80% of cancers were found following a FIT result greater than the new threshold level, with almost 60% found with a FIT test reading 1000ng or higher.

The changes to the age range and the test threshold would maximise the number of cancers and advanced adenomas detected while reducing the required number of screening colonoscopies, Prof Parry said.

''This would reduce risk for participants and bring screening colonoscopy delivery to a level that better matched capacity.''

What this approach overlooks is what Dr Paul Pinsky, of the National Cancer Institute of Bethesda, so eloquently stated in a Lancet opinion piece earlier this year, that colorectal cancer is largely a preventable disease.

''As with cervical cancer, the ability to reduce incidence as well as mortality through minimally invasive removal of precursor lesions is a gift of nature that should be taken advantage of if at all possible,'' he wrote.

If there are fewer colonoscopies being done, any risk from this invasive procedure might be reduced, but the likelihood of precursors to cancer being found and snipped off is also reduced, simply because many people who could be harbouring precancerous growths will never have their bowel examined.

Given the choice, many people might consider the benefits associated with someone actually looking at what might be in the colon outweighed the risk of the procedure.

It was considered introducing a national programme with the same age range and positivity threshold as the pilot would overwhelm New Zealand's colonoscopy resource.

There is no denying colonoscopy capacity is a major issue affecting what can be offered, but why is it taking so long to address this? As Bowel Cancer New Zealand spokeswoman Associate Prof Sarah Derrett says, policy-makers have known about these limitations for decades ''and yet action has been lacking''.

Her organisation is unhappy about the age range and the threshold level.

''Bowel cancer is detectable, treatable and beatable if caught in time - and that is where BCNZ knows the need for a national screening programme including people in their 50s, and with a sensible threshold, is paramount.''

At this stage there does not seem to be a clear plan for improvements to the programme.

Prof Parry says outcomes in the national programme will be monitored very closely and there is a possibility the threshold for positivity of the FIT will be raised or lowered as required in the future.

In a Government obsessed with targets, why hasn't a date been put on when we might expect something better?

Has proper attention been paid to large-scale research around the use of flexible sigmoidoscopy (a procedure similar to a colonoscopy but which examines the lower part of the bowel and requires less bowel preparation) as a screening test, which shows promising long-term preventive results? In Britain, a one-off flexi-sig procedure is now being offered to screening participants in their 50s, as part of its programme.

A forward-thinking approach in New Zealand might have been to spend some years training general practitioners and endoscopy nurses to carry out flexible sigmoidoscopies, getting them up to speed on quality and with the Government putting up some money to improve practice facilities to allow for this. Would mobile flexi-sig theatres be an option?

While some participants would still require colonoscopy, which examines the whole bowel, the number of referrals for this would be much reduced.

There seems to have been continued resistance to this, which has seen the sidelining of Prof Cox, who for years has seemed like a one-man band giving consistent and evidence-based arguments for including a one-off flexible sigmoidoscopy in New Zealand's programme.

He considers flexible sigmoidoscopy, offered once between the ages of 55 and 64, would be by far the most cost-effective strategy for reducing the disease in New Zealand.

He sees the New Zealand programme as a ''poor gamble'', as the FIT screening would provide no appreciable reduction in bowel cancer risk, while a one-off flexible sigmoidoscopy would reduce subsequent lifetime risk of cancer by 35%. Mortality from the disease would also be reduced by 41%.

The published results of the large-scale UK trial (which involved the screening of more than 40,000 people) confirmed reduced bowel cancer incidence and mortality persisted for at least 17 years after the flexi-sig.

Such screening would mean much less surgery for bowel cancer and savings from treatment cost could be used to fund a national flexi-sig screening programme.

In a recent visit to the United Kingdom, Prof Cox looked at the way flexi-sig screening worked in the programme there.

He estimates that a one-off flexi-sig at the age of 55 here, screening half the total population of that age, would involve carrying out 27,500 flexi-sig procedures a year.

This would require 19 screeners each doing three and a-half lists a week. (In the UK programme about 1500 flexi-sig procedures is a practicable load for a screener).

This screening would generate a colonoscopy list about every fortnight, he says.

The decision not to use flexi-sig as part of the Waitemata screening pilot allows Prof Parry to be able to argue now that using flexi-sig would delay implementation of a national programme by several years because of the need for extensive workforce training to ensure quality and extra resources, including theatre space.

Another concern is the insufficient resourcing of stretched DHBs to carry out the extra work associated with the programme.

In information released to the Otago Daily Times under the Official Information Act recently, Southern DHB indicated doing the extra surgery from within existing budgets, as it appears boards will be required to do, would come at a cost to other patients.

For a screening programme to be successful, every aspect of it has to work well or there will be shortcomings which make it unsafe or which could result in people losing confidence and being reluctant to participate.

These aspects include choosing an effective test, information for participants, the reading of the test, the communicating of results, the referral for whatever further investigation or treatment is deemed necessary (e.g. colonoscopy, surgery, chemotherapy, ''watch and wait''), the diagnostic tests and treatments themselves, the follow-up of all of those things, and independent effective ongoing evaluation of the programme to ensure quality and timeliness at every part of it.

This one has not got off to a good start.

-In 1998, Elspeth McLean's husband, Ken, died of bowel cancer when he was almost 49. In common with many colorectal cancer patients, his condition was first diagnosed after an urgent hospital admission.

Mrs McLean has closely followed the moves towards national screening and wrote extensively about the issues, including colonoscopy capacity, during her time as an Otago Daily Times health reporter several years ago.

 

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