Although its preventable through screening, bowel cancer is the third most common cancer in the UK.  Each year, more than 36,500 people are diagnosed with the disease and around 16,000 people die of bowel cancer each year in the UK.

One in twenty people will develop bowel cancer at some point in their life.  Nine out of ten people with bowel cancer detected at an early stage survive for more than five years, however, if the tumour is very advanced when it's found, fewer than one in twenty people survive, which builds a powerful case for early screening for the disease.

Research published in The Lancet covering a randomised trial population of over 170,000 patients has definitively shown that a quick, one-off screening test saves lives.

Although 97% of all diagnosed cases are in people over 50, the NHS national bowel cancer screening service (introducted in 2006) applies to those aged 60-69, which also uses a different screening test, a Faecal Occult Blood Test.  The latest research covered flexible sigmoidoscopy, so we've provided a summary of the different testing approaches below, along with the advantages and disadvantages of each type of test.

Faecal Occult Blood test (FOB) - looks for blood in faeces, a very simple and inexpensive test.  However, the weakness of the test is that it's not very sensitive or specific for cancer, as many patients with cancer or large polyps (which can grow into tumours) don't have blood showing in the stool.  Many patients who have a positive test result will have no colonic problem, so may have had further unnecessary tests and anxiety.

Flexible sigmoidoscopy - an endoscope (thin, flexible tube with a miniature video camera on the end) is passed through the anus to examine the rectum and first part of the colon.  The test requires a cleansing enema prior to attending a hospital.  Although the test is highly sensitive and specific for cancer or polyps, the test only examines about 1/3 of the colon, so cancers and polyps higher in the bowel can be missed.

CT (virtual) scan - CT (X-Ray) scanning images the entire bowel.  The test screens the whole colon in a couple of minutes, although also requires a cleansing enema.  Although relatively quick, air needs to be pumped into the anus before the test, so it is not without discomfort.  The test is highly accurate, although cannot remove or biopsy any polyps or tumours that are found, so positive findings would usually lead to conventional colonoscopy to biopsy any suspected cancers.

Colonoscopy - an endoscope is passed all the way around the colon to directly visualise all areas where polyps and cancer can occur.  The test requires a cleansing enema prior to attending a hospital.  Patients are usually offered sedation if they want it, though at least 50% of people can have colonoscopy without, meaning some people can return to normal life quickly.  The test can only be done in an Endoscopy Unit.

Considering the various approaches, Blossoms suggests that colonoscopy is the most appropriate screening test for bowel cancer, as although preparation is required, if any polyps or cancer are detected, they can be biopsied or removed at the same time, so colonoscopy is definitive, combining diagnosis with treatment in one procedure.

Sources:

http://info.cancerreasearchuk.org/cancerandresearch/ourcurrentresearch/researchbycancertype/bowelresearch_new/index.htm#Screening.

http://www.cancerscreening.nhs.uk/bowel.

http://info.cancerresearchuk.org/spotcancerearly/screening/bowelcancerscreening/index.htm.

http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2810%2960551-X/fulltext