Bowel cancer screening - Treatments

Faecal occult blood test

There is good research to show that this test works for bowel cancer screening. People who have it once a year or once every two years, with a follow-up colonoscopy if the results are positive, are less likely to die of bowel cancer. It is called an occult blood test because blood may be hidden in your stools (the word 'occult' can mean 'hidden').

One summary of the research (called a systematic review) found three large good-quality studies (called randomised controlled trials). The studies looked at what happened to people who had a faecal occult blood test (FOBT) every one or two years, compared with people who had no screening, over a period of 8 to 13 years:[1]

• In one study of 46,000 people, there were about one-third fewer deaths from bowel cancer in people who had annual FOBT screening for 13 years, compared with people who had no screening.[2]
• In one study of 62,000 people, there were about one-fifth fewer deaths from bowel cancer in people who had FOBT every two years for 10 years, compared with people who had no screening.[3]
• In one study of more than 150,000 people, there were about 15 percent fewer deaths from bowel cancer in people who had screening every two years for about eight years, compared with people who had no screening.[4]

None of these studies showed that screening helped to stop people from getting bowel cancer. They just showed that people who'd had screening were less likely to die from bowel cancer.

FOBT screening can give false-positive results (when the test shows you have cancer, but you don't). The studies we found did not look at how often this happened, so we don't know how big a problem this was.

But we do know that most people who have a positive FOBT will not have cancer. This is because there are lots of other medical problems that cause bleeding from the back passage.[5]

Research has shown that people don't always find it easy or pleasant to do this kind of home testing.[6]

Between 4 and 6 in 10 people taking part in these studies dropped out before the end. This may be because they found it difficult to do the testing or found it unpleasant.

Flexible sigmoidoscopy

There is quite a lot of evidence to show that this test works for bowel cancer screening. People who have a flexible sigmoidoscopy test are probably less likely to get bowel cancer.

We found one small good-quality study (called a randomised controlled trial) comparing sigmoidoscopy with no screening in 799 people.[7] Half the people in the study had one sigmoidoscopy test. If the test showed they had polyps, they were then given an immediate colonoscopy test. These people then had repeat colonoscopies two and six years later.

Thirteen years after the study started, the study found:

• 2 in 400 people screened by sigmoidoscopy had developed bowel cancer
• 10 in 399 people who were not screened at all had developed bowel cancer.

No one in the study was harmed by having sigmoidoscopy. But another, bigger study showed some people having sigmoidoscopy were had problems with the test.[8] Of 40,674 people screened with flexible sigmoidoscopy:

• Five got a torn (perforated) bowel: one from sigmoidoscopy and four from follow-up colonoscopy
• 12 were admitted to hospital with bleeding: three from sigmoidoscopy and nine from colonoscopy.

In another study of 9,911 people having a single sigmoidoscopy test, just one person got a torn bowel. After sigmoidoscopy, 775 people went on to have colonoscopy. This caused one torn bowel and one case of serious bleeding.[9]

All three of these studies looked at how people felt about the test:

• At least half found the test uncomfortable
• 1 in 20 people found the test embarrassing.

Some people believe that screening makes people more anxious about cancer. But one study found that people who were offered sigmoidoscopy screening and sent written information about bowel cancer were less likely to feel worried about bowel cancer than those offered no screening or information.[10]

Colonoscopy

Colonoscopy is a very good test for diagnosing cancer. But there's not enough research to say if it is a good screening test. And we don't know if the risk of harm from having this test outweighs the benefits.

There haven't been any good-quality studies that look at whether using colonoscopy for screening helps to prevent bowel cancer or reduces deaths from bowel cancer.

One summary of the research (a systematic review) found two studies that looked at whether people were likely to be harmed by having colonoscopy for bowel cancer screening.

In one study of 3,121 people having colonoscopy, six people had serious bleeding and four others had serious complications.[11]

In another study of 1,994 people having colonoscopy, three people had bleeding so bad that they had to go to the hospital emergency department.

Colonoscopy is a very thorough test for bowel cancer, because it can see the full length of the bowel. That's why doctors use it if you have had a positive result on another test.[12] But the most thorough test is not always the best test to use for screening large numbers of healthy people.

More studies need to be done before we know whether the benefits of using colonoscopy for screening are worth the risks of harm.

Combination of faecal occult blood test and flexible sigmoidoscopy

We know that a faecal occult blood test and flexible sigmoidoscopy work well when they are done separately.[1] [7] But we don't know if they help to prevent bowel cancer or cut deaths from bowel cancer when used together.

There hasn't been any good-quality research comparing having a combination of these two tests with having no screening at all. And we don't know whether using them together is better or worse than using them separately.

The problems with the tests used separately are also likely to apply to using them together. These include:

• A false-positive result (when the test says you have cancer but you don't)
• A small chance of damage to your bowel.

Computed tomography colography

We don't know if computed tomography colography works for bowel cancer screening. There haven't been any good-quality studies to show whether it helps prevent bowel cancer or cuts deaths from bowel cancer.

Double-contrast barium enema

We don't know if double-contrast barium enema works for bowel cancer screening. There haven't been any good-quality studies to show whether it helps to prevent bowel cancer or cuts deaths from bowel cancer.

One summary of the research found that the test detected between 62 percent and 100 percent of bowel cancers. But this research looked at how good the test was in people who were at a high risk of getting bowel cancer. If you are not at high risk, the results may not apply to you.