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Faecal occult blood test and bowel cancer screening

As the colorectal cancer screening programme expands, pioneer Dr Richard Tighe explains the clinical evidence on which it is based and the likely implications for GPs

As the colorectal cancer screening programme expands, pioneer Dr Richard Tighe explains the clinical evidence on which it is based and the likely implications for GPs

Why was a screening programme needed?

Bowel cancer develops from adenomatous polyps in the colon which have often been present for five to 10 years before malignant transformation. Removing these polyps before malignant change prevents the development of cancer.

A review of survival from bowel cancer in 2004 found that the UK had the lowest survival rates in Europe, and that this high mortality was largely related to late diagnosis, identifying the need for a programme that could screen for early disease.

Although the first large-scale trials of faecal occult blood (FOB) as a screening tool were carried out in the 1980s, the evidence of long term benefit took time to accrue.

What were the results of the trials?

In the 1980s, large-scale trials were undertaken to assess whether FOB testing of asymptomatic people could be useful in detecting individuals with early bowel cancer. In total 330,000 people were enrolled in four trials, the largest of which was conducted by the MRC in Nottingham. The trials studied FOB testing on annual or biannual strategies using non-hydrated or rehydrated Guaiac haemoccult tests – with colonoscopy or barium enema imaging of the colon for people with abnormal FOB. These trials were conducted over 10 years and have been subjected to long-term follow-up and analysis.

The trials found:

• uptake in trials is around 60%

• sensitivity for non-rehydrated FOBT is around 55% for cancer

• sensitivity of rehydrated FOBT is higher (82-92%) but at the cost of reduced specificity (more false positives)

• biannual testing is as effective as annual testing

• screening of asymptomatic 55-75-year-olds reduces mortality from bowel cancer by 16% overall, or by 25% in those 60% of individuals who return an FOBT

• there was no reduction in all-cause mortality from FOB screening.

From 2000 to 2005, a large-scale pilot study was conducted in England and Scotland to examine the feasibility of population screening, and ensure the trial results could be reproduced in everyday practice. The results matched the trial meta-analysis data.

Uptake and pathology detection was significantly lower below the age of 60, while the complications of colonoscopy examination remain more or less the same at all ages. The reduction in mortality from bowel cancer achieved by FOB screening by age is 0.8/10,000 at age 40 to 49; 3.5/10,000 at age 50 to 59 and 11.2/10,000 for those aged 60 to 69. A decision was therefore made to concentrate FOBT population screening on the 60 to 69-year-old age group in England with an opt-in arrangement for the over-70s.

What is the current situation?

The NHS bowel cancer screening programme started in England in July 2006 and is being rolled out in three waves to cover 25%, 50% and 100% of the population.

To reduce the potential effect on primary care, five supraregional hubs have been established (Warwick, Nottingham, London, Guildford and Gateshead). These are responsible for inviting people to join the programme from local Exeter databases, sending out and analysing FOB kits, and organising investigation of abnormal results.

Each hub relates directly to bowel cancer screening centres responsible for the colonoscopy investigation and organising subsequent management. Each screening centre covers a population of up to 2 million people and there will be about 90 screening centres in England (from 300 secondary care endoscopy units). The screening centres have taken on specialist nurses who have been trained on the intricacies of the programme and on the assessment of people prior to further studies. These specialist nurses answer the questions that would otherwise be directed at primary care. All screening centres and their endoscopists have undergone strict quality assurance assessments (peer review visits and accreditation of colonoscopists) in an effort to try to minimise the negative aspects of screening (such as complications of the colonoscopy).

In July 2006, the first two screening centres in Wolverhampton and our own in Norwich went live and 10 other centres followed later in the year. The Norwich plan involved initially screening a population of 550,000 from central Norfolk with an anticipated 65,000 in the 60 to 69-year-old age group.

Uptake from the public has been high at 70% and approximately 2% of FOB tests have been abnormal. Attendance for further investigation (colonoscopy) is 98%. Cancer detection rates are 17%, of which 40% have been early polyp cancers. A further 45% of colonoscopies have revealed adenomas, whilst 34% have been normal.

All patients referred with an abnormal FOB test are seen initially in the clinic by a specialist nurse within 10 days of the FOB result, and undergo colonoscopy within two weeks of the nurse assessment clinic. They are contacted after the colonoscopy by the specialist nurse – first to check there have been no problems post-procedure and later to give results of any samples removed. Cancer patients are fed direct into the colorectal cancer pathway and discussed at the multi-disciplinary team meeting after staging.

What impact has this had on secondary care and in particular the symptomatic endoscopy service?

Additional colonoscopy lists were established to manage the demand from the screening programme and there has been no impact on the symptomatic service – with waits for all routine endoscopy procedures at four weeks or less.

How does this effect general practice?

The invitation to join the programme and delivery of an FOB kit are not requested by the target population and arrive unannounced. The letters are accompanied by an information pack, but some people may wish to discuss with their GP whether to take part. The pack also includes a freephone number (0800-7076060) for the public to contact to discuss the issues further.

In general we would not advise patients already in a colonoscopy surveillance programme, or who have had a recent colonoscopy (within two years) to take part.

No dietary restriction is required and people can continue aspirin, NSAIDs and anticoagulants whilst undergoing FOB testing.

The FOB test has a sensitivity for bowel cancer of only 55%. We would therefore advise that all patients with large bowel symptoms are referred to their local hospital for assessment and investigation along standard lines, rather than relying on the FOB test to exclude pathology.

We would advise investigation of symptoms as appropriate and with colonoscopic screening for high-risk groups – such as those with family history of bowel cancer, long history of inflammatory bowel disease, previous adenomas.

How do GPs find out about their patients' results?

All communications to the patient about the results of FOB testing, and subsequent colonoscopic examinations are copied to the family doctor.

Will we receive feedback on uptake in our area?

It is hoped that, following an IT update, details of uptake by locality will be available from September to enable more intensive publicity.

The future

Screening tests with a greater sensitivity and specificity for high-risk polyps and cancer are being considered for use in the bowel cancer screening programme, though none have currently been subjected to trials to demonstrate improvement in mortality.

Two studies are due to report in 2008: a 10-year follow-up study of flexible sigmoidoscopy screening in 60-year-olds and a study comparing flexible sigmoidoscopy and CT colonography. Either of these techniques, however, would take some time to introduce as a mass screening tool.

In the meantime, FOB testing is proven to reduce colorectal cancer mortality and will continue for the foreseeable future.

R

  • ichard Tighe is a consultant gastroenterologist at the Norfolk and Norwich University Hospital and clinical lead for the bowel cancer screening programme in the East of England

Competing interests None declared

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