Colorectal Cancer Screening
What is the National Bowel Screening Programme?
Around 1 in 20 people will develop colorectal cancer. Since these cancers tend to grow slowly, arising from polyps it is possible to identify a great many patients when their tumour is at an early stage. The government has expanded a programme of screening for colorectal cancer to the general population. People aged 55 will be offered a single telescopic examination of the colon (a flexible sigmoidoscopy). This looks at the left side of the colon since statistically this is where the majority of cancers arise. If an abnormality is detected on this test they will be offered a further test (a colonoscopy), which will look at the the whole of the colon.
People between the age of 60 and 69 will be invited to submit a stool sample for testing every 2 years. This is known as faecal occult blood testing (FOB) and looks at the tiny quantities of blood that these growths produce. Those over the age of 70 will be able to undergo the test if they wish but will have to contact their local doctor. Around 98 people in every 100 screened will have a normal result, of these 4 will be unclear and people will have to repeat the test. Two in every 100 will have an abnormal test and will be advised to undergo a colonoscopy evaluation of the colon (bowel). Half will have nothing seriously wrong but may have a simple condition such as haemorrhoids, 4 in ever 10 will have a polyp that may be removed and 1 will have a cancerous growth. Of those with cancer studies have shown that 2/3rd of are at a very early stage amenable to cure. For ore information visit the national screening web site www.cancerscreening.nhs.uk/bowel/. It must be remembered that a normal FOB test does not absolutely guarantee that there is no cancer or polyp present although it makes it extremely unlikely and the development of any new symptoms such as rectal bleeding, an alteration in bowel habit or tiredness and lethargy warrant consultation with your doctor.
Are there patients with a particularly increased risk of developing bowel?
A number of people have an increase risk of developing bowel cancer, they should be considered for inclusion in a screening programme and include
Inflammatory bowel disease
Patients who have longstanding ulcerative colitis or Crohn’s disease affecting the colon have an increased risk of developing colorectal cancer and are advised to undergo regular colonoscopy. The frequency of this depends partly on the length of time that they have had the condition and the extent to which it affects the colon. Patients with disease affecting the entire colon should begin colonoscopy surveillance after 8 years whilst those with disease affecting just the left side should undergo colonoscopy after 15 years. After this, colonoscopy should continue every 3 years until they have had the condition for 20 years, it should then become every 2 years until they have had the condition for 30 years and should then move to annually.
Family history of colorectal cancer
Up to 20% of colorectal cancer may have some genetic component although less than 5% will have an identifiable genetic defect. Patients from a family thought to have a genetic condition that pre-disposes to the formation of colorectal cancer such as familial adenomatous polyposis (FAP) or hereditary non polyposis colon cancer (HNPCC) should be evaluated by a genetics specialist and offered surgery or entered into a screening programme if appropriate. It must be stressed that the majority of patients do not have these conditions but the risk of developing a bowel cancer increases with the number of family members who have developed these cancers. These people benefit from colonoscopic surveillance but should see their local doctor for further evaluations by someone who understands the genetic risks associated with colorectal cancer and will refer them to a specialist clinic if there is any doubt (see inherited colorectal cancer).