Bowel cancer is the general term for cancer that begins in the large bowel. Depending on where in the bowel the cancer starts, it is often referred to as either colon cancer or rectal cancer.
It is held that two thirds of bowel cancers develop in the colon with the remaining third developing in the rectum. Cancer can also sometimes start in the small bowel (small intestine), though this is much rarer than large bowel cancer.
The Large Bowel
The bowel is part of the digestive system and has two main functions:-
-to absorb energy, water and nutrients from the food you eat
-to pass out the remaining waste products from the body via stools
The bowel is made up of five sections:-
-The ascending colon: runs from the end of the small intestine and up the right-hand side of the abdomen.
-The transverse colon: runs under the stomach and across the body from right to left.
-The descending colon: runs from the left-hand side of the abdomen
-The sigmoid colon: an ‘S’ shaped bend that connects the descending colon to the rectum.
-The rectum: the final section of the bowel. This is a small pouch that is connected to the outside opening of the bowel (anus).
Early bowel cancer may not have any symptoms at all. If it does, some initial symptoms may include:-
-Blood in stools or bleeding from the rectum
-A change to normal bowel habits that persists for 6+ weeks.
-Unexplained weight loss
More advanced bowel cancer can cause bleeding from inside the bowel. This can lead to anaemia which will present symptoms as fatigue and breathlessness.
Bowel obstruction can also occur in individuals with more advanced bowel cancer which can cause constipation and if left untreated, can lead to perforation of the bowel.
Cancer occurs when the cells in a certain area of the body, in this case the bowel, divide and multiply too quickly, producing a lump of tissue known as a tumour. Most cases of bowel cancer first develop inside clumps of cells on the inner lining of the bowel, known as polyps, and they do not necessarily turn into bowel cancer.
The exact cause of bowel cancer remains unknown, although there are thought to be several risk factors increasing the chance of getting it including:-
-Diet: a diet high in red and processed meat. Equally, a diet high in fibre and low in fat can help reduce the risk. The logic behind this is because this type of diet encourages frequent and regular bowel movements, thought to keep the bowel healthy.
-Smoking: people who smoke cigarettes are 25% more likely to develop bowel cancer.
-Alcohol: an EPIC study (European Prospective Investigation into Cancer and Nutrition) has shown that for every two units of alcohol that a person drinks every day, their risk of bowel cancer increases by 8%.
-Obesity: it has been reported than obese men are 50% more likely to get bowel cancer than men of a healthy weight.
-Genetics: bowel cancer may also have a genetic link. It is reported that 20% of those with bowel cancer have a close relative or second-degree relative with the disease.
-Digestive disorders: people who suffer with Crohn’s disease are 2-3 times more likely to get bowel cancer and 1 in 20 suffers of ulcerative colitis have bowel cancer.
Bowel cancer is usually diagnosed by the aforementioned symptoms. If you are presenting symptom and have a family history, it is likely that your GP will make a referral for a Digital Rectal Examination.
The GP can also perform checks for a noticeable lump inside the rectum found in 40-80% of bowel cancer cases. If the lump is found, a referral will be made for a Sigmoidoscopy or Colonoscopy which are ways of looking into the bowel via cameras. These methods are also used to take a biopsy if necessary.
NHS Bowel Screening Programme
In 2006, the NHS launched a screening programme where individuals aged 60-69 are screened for bowel cancer every 2 years. This was extended in 2010 and is now offered to individuals over 55 as a ‘one off’ scope screening test. Individuals aged 60-74 will then be invited to do a home testing kit every two years.
The test is completed by taking a small stool sample and testing it for the presence of blood. Two individuals out of 100 will have an abnormal result and will be referred for a colonoscopy. Out of the cases referred for colonoscopies, 1 in 10 individuals will have bowel cancer.
Staging and Grading
The staging of cancer is how far advanced it is and the grade given is how aggressive the cancer and how far it has spread to surrounding areas.
Stage 1: the cancer is contained within the lining of the bowel/rectum.
Stage 2: the cancer has spread into the layer of muscle surrounding the bowel.
Stage 3: the cancer has spread into nearby lymph nodes.
Stage 4: the cancer has spread into another part of the body, such as the liver.
The stages are often divided up further into A and B.
Surgery is the most common way of treating bowel cancer although 1 in 5 cases are too advanced to be removed by surgery alone. If surgery cannot remove all of the cancer, chemotherapy, radiotherapy and biological therapy may be used as well.
Surgery offers a good cure for cancer although it is not possible to cure Stage 4 cancer that has spread into surrounding organs.
As with most cancers, the outlook depends largely on how far the cancer has advanced by the time it is diagnosed. If the cancer is diagnosed early, the chance of living for a further 5 years or more is 90% and usually, a complete cure is possible.
If the cancer is diagnosed in the more advanced stages, there is a 6% 5 year survival rate and a complete cure is highly unlikely.
In England, bowel cancer is the third most common type of cancer diagnosed.
There are 38,000 new cases diagnosed every year.
Bowel cancer is most common in those over 60 accounting for 80% of cases diagnosed.
16,000 people die from bowel cancer annually in England alone.