DCSIMG

Good results for bowel cancer testing

“A bowel cancer screening programme in England is on course to cut deaths by a sixth,” the BBC has reported. The story goes on to say, however, that there is concern “that the programme misses tumours in certain parts of the colon”.

This story is based on analysis of the first round of England’s Bowel Cancer Screening Programme, which was introduced in 2006. Screening programmes are designed to test for signs of a disease among people without symptoms. They can often detect diseases early, allowing treatment to be given at a stage when it is more likely to be effective at improving outcomes and lowering the risk of death. The screening programme invites people between the ages of 60 and 69 to participate, by giving them home faeces sampling kits that can be posted to a lab to check for traces of blood. Those who screen positive at this stage are then invited to undergo further diagnostic tests.

To date, the programme has invited about 2 million people to participate, with around half accepting and returning a sample. The results of the analysis suggest that if the early results are maintained, the screening programme will achieve the intended 16% reduction in overall bowel cancer deaths.

 

Where did the story come from?

The study was carried out by researchers from the University of Nottingham, University College London and bowel cancer screening centres throughout the UK. The authors do not state any sources of funding but say that their research was not commissioned.

The study was published in the peer-reviewed medical journal, Gut.

The BBC reported on this study appropriately, although headlines saying that the programme “does cut deaths” may be premature, as the research has not yet examined the impact the relatively new screening programme may have on bowel cancer deaths. The news story does go on to clarify that the programme is “on course to cut deaths” based on the results of the first 1 million participants.

 

What kind of research was this?

This was a report on the uptake and early outcomes of England’s Bowel Cancer Screening Programme introduced by the Department of Health in 2006. Previous research has indicated that introducing a screening programme could reduce bowel cancer deaths by 16% in the people invited to participate in the programme, and by 25% among those who accept their invitation and participate in the programme. This research aimed to compare the uptake and outcomes to these estimates.

Bowel cancer is the second leading cause of cancer deaths in the UK, with 16,000 deaths a year. Only 50% of those diagnosed are still living five years after their diagnosis, in part due to the late stage the disease is generally diagnosed at. Earlier detection of cancers generally allows more options for treating them, and screening programmes that increase the proportion of cancers detected early may improve survival. Thus, it is important to continually monitor the success of screening programmes, both in terms of the way they encourage at-risk groups to be checked and in the number of lives they save.

 

What did the research involve?

The programme used the National Health Application and Infrastructure Services system to identify people eligible for the screening programme. Around 80% of bowel cancer cases are in people aged 60 and above, and so the screening programme was aimed at men and women ages 60 to 69 years old that were registered with a GP. They were invited to participate in the programme around the time of their birthday and every two years until they they reach the age of 70.

The bowel cancer screening programme uses a test called the ‘guaiac faecal occult blood test’, which looks for the presence of blood in a faeces samples. As part of the screening process, invitees are sent a letter describing the screening process, followed by an at-home sampling kit, which they use and then mail back to the programme hub. The test kit contains six windows, and participants are asked to take two small faecal samples from three separate stools and place them into the windows. The kits are then returned by mail, and are analysed to detect for bleeding in the colon. Those participants that screen positive for blood in their stools are invited to attend a follow-up appointment where they will be offered further diagnostic tests, generally colonoscopy (where a small camera on a thin, flexible tube is used to examine the inside of the colon). In borderline cases some participants were also asked to provide another set of samples.

Between July 2006 and October 2008, the programme sent out 2.1 million invitations to participate. The researchers analysed how many of these invitees accepted the invitation and participated in the programme, and how such uptake varies across postcode sectors. Postcode and demographic data was used to analyse patterns in uptake, and to identify factors such as social status that are associated with participation in the screening programme.

 

What were the basic results?

When the researchers looked at uptake, they found that:

  • 52.0% of those invited returned test kits (1.08 million).
  • There was a significant difference in uptake between men and women, 49.6% of the invited men, compared to 54.4% of the invited women.
  • There was a significant difference in uptake across socioeconomic groups, with an uptake of 61.4% in the least deprived group, compared to 41.7% in the most deprived group.
  • Uptake was highest in the North East and lowest in London. This pattern held between the sexes and across socioeconomic groups.

When the researchers looked at screening test results, they found that:

  • 2% of the participants had a positive (abnormal) test result for blood in their faeces.
  • There was a significant difference in the proportion of participants returning a positive test between the sexes, with 2.5% of men having a positive test, compared to 1.5% of women.
  • Of those returning a positive test, 94% attended a follow-up appointment at a specialist centre to receive their test results and be invited to undergo further diagnostic tests.
  • Among the 94% attending a follow-up appointment, 83% opted to undergo the further tests; 7.6% of attendees were deemed to not need further tests, and 3.7% decided not to participate.

When the researchers looked at the results of further diagnostic tests, they found that:

  • Of those participants who returned abnormal screening tests, 98.1% received a colonoscopy as the first diagnostic test.
  • 10.1% of participants were diagnosed as having bowel cancer; 11.6% of men and 7.8% of women.
  • A further 12% of men and 6.2% of women were found to have high-risk adenomas, a type of benign tumour that can become cancerous. They were invited to undergo another colonoscopy in one year, as per screening surveillance guidelines.
  • A further 19.3% of men and 14.6% of women were found to have intermediate-risk adenomas, and were invited to undergo another colonoscopy in three years, according to surveillance guidelines.
  • In total, 43% of men and 29% of women who returned a positive screening result were found to have either bowel cancer or precancerous cells that required treatment or close surveillance.

Among the cancers identified through a positive screening test and further diagnostic testing:

  • 71.3% of the cancers were potentially curable polyps or early stage disease.
  • 77.3% were left-sided, and 14.3% were right sided; this was a lower proportion of right-sided cancers than expected. Right-sided bowel cancers tend to be larger and at a more advanced stage before causing any symptoms. A screening programme that could detect them early could potentially improve outcomes for these patients. Researchers say this result may be because right-sided tumours must be larger than those on the left side before producing enough blood to be detected by this test.

 

How did the researchers interpret the results?

The researchers say that most of their results were in line with previous pilot projects and the targets set out at the start of the screening programme. However, regional differences in uptake and the lower percentage of cancers found on the right side were unexpected. They say that it is unclear at this stage whether the low numbers of right-sided cancers detected are due to the screening technique or the natural course of the disease.

 

Conclusion

This analysis of a relatively new screening programme demonstrates that the programme has been effective in detecting bowel cancers at an early stage. This is extremely important in this disease, as in the absence of an effective screening programme most cases would not be diagnosed until they have progressed considerably. At this point treatment becomes more difficult, and survival is less likely than those cases diagnosed at an early stage.

The researchers say that uptake of the programme outside of London was very good, and high by international standards. The study also revealed unexpected variations in participation across regions and socioeconomic levels. Knowledge of such variation is essential, as it allows programme administrators to alter their recruitment and invitation techniques in order to ensure that more people participate in the programme. For example, it could allow targeted advertising in regions with low uptake or more favourable ways for contacting targeted groups.

This research presents a snapshot of how the early years of the screening programme have progressed, and further follow-up will be needed to determine if the new screening programme has the expected longer-term impact on bowel cancer deaths. Additionally, this was analysis of the first round of the programme, which was designed to detect cases that already exist in the population. Further rounds will aim to detect new cases, so it is not yet clear whether the programme will be effective to this end as well.

Screening programmes are large, potentially expensive and can be difficult to manage. It is therefore extremely important to ensure that programmes are having an impact on the number of cases of disease being detected and improve the outcomes of subsequent treatment. Although mass screening can be costly and resource-heavy, it should be remembered that the cost of well-designed and efficient programmes can be offset by early detection of diseases that are difficult, and even more costly, to treat at later stages.

Screening programmes are complex to evaluate, but this initial round of results from the screening programme indicate that England’s Bowel Cancer Screening Programme is detecting a higher number of early stage colon cancers than would be detected otherwise. In time, we can see whether this translates into fewer deaths and better outcomes in the long term.

 

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