Bowel Cancer

When we talk about ‘bowel cancer’ we normally mean cancer affecting the large intestine – the colon and the rectum. Unfortunately bowel cancer is one of the more common cancers and many of us know 1 or more family members or friends who have been affected by bowel cancer.

Whenever people come to see me with their tummy symptoms, many of them worry about the possibility that they could be due to bowel cancer. Of course, tummy symptoms are common – we have all experienced them from time to time. The vast majority of tummy symptoms do not have a sinister cause – but that knowledge doesn’t stop people worrying about what might be going on inside their tummy. Yet we often just put up with our symptoms. We may not want to make a fuss or we might be afraid of seeking medical help. Hospitals and clinics can feel like scary places. We may be frightened of the thought of what sort of tests the doctor may recommend or even what the tests might show.

I am going to give you all the information you need about bowel cancer (colon cancer and rectal cancer) and explain how specialists diagnose and investigate it.

How common is bowel cancer?

Unfortunately bowel cancer is one of the more common types of cancer – it is the 3rd most common type of cancer in both men and women. The rates of bowel cancer have been slowly rising over the last 10 years. Approximately 1 in 14 men and 1 in 19 women will develop bowel cancer during their life. On average, around 110 new cases are diagnosed each day in the UK.

Bowel cancer is also the 2nd commonest cancer that people in the UK will die from. The good news is that death rates from bowel cancer are falling – due to better detection and better treatments.

It is really important that bowel cancer is diagnosed as early as possible – the earlier it is found, the more curable the cancer is. Once the cancer has grown and started to spread outside of the bowel, it is much more difficult to cure. Because of this, if you are worried that your tummy symptoms might be due to bowel cancer, it is important to see your GP or a specialist as soon as possible

What is the large intestine?

The large intestine connects your small intestine to the back passage (anus) and is the final part of the digestive tract. The large intestine is often called the colon – although strictly speaking the rectum (the very end part of the large intestine) is not part of the colon. The shape of the colon is a bit like an upside-down ‘U’. The small intestine joins the large intestine at the bottom right of your tummy at the ileo-caecal valve, close to the appendix. The large intestine can be sub-divided into the caecum, the ascending colon, the transverse colon, the descending colon, the sigmoid colon and the rectum.

How does bowel cancer develop?

Most bowel cancers start off as a tiny polyp (adenoma) in the wall of the colon or rectum. A polyp is caused when a cell in the inside lining of the bowel undergoes a mutation and starts to grow and divide faster than the surrounding cells. In time the group of more rapidly growing cells starts to become heaped up causing a small ‘lump’ to form on the inside surface of the bowel. Over time polyps can continue to grow and may develop a stalk and a head which looks like a small mushroom growing from the lining of the bowel.

Most polyps do not cause any symptoms. Most polyps are completely benign and will never develop further. However if more mutations occur to one of these rapidly growing cells, there is a small chance that over time the polyp can become cancerous.

Cancerous cells grow and divide much more rapidly than the surrounding cells. In the colon this can eventually cause a narrowing or in advanced cancer a complete blockage to the bowel. Cancerous cells can also invade through the wall of the colon to the outer surface of the bowel wall. Once this occurs, they can be carried in the blood stream or via lymph nodes to the liver.

I talk more about lifestyle changes that can reduce your risk of developing bowel cancers later on in this article.

What are the symptoms of bowel cancer?

Early bowel cancer can often cause only subtle or minor symptoms and so it is important to be alert for changes. As the cancer grows symptoms can be become more marked and obvious. Important symptoms to look out for include:

  • Blood in the poo. Bleeding – particularly on wiping after having a poo – is quite a common symptom that many people experience at one time or another. The majority of cases of rectal bleeding are due to haemorrhoids. However bowel cancer and large polyps can also cause blood in the stool and so any unexplained bleeding is worth mentioning to your doctor. It is particularly important to see your doctor or to make an appointment to see a specialist if you also have any other symptoms such as looser or more frequent stools, tummy pain or weight loss. I talk more about the causes and investigation of blood in the poo here.
  • Looser poo or having to go to the toilet more often. Most of us have suffered from diarrhoea at one time or another, or have had times when we end up going to the toilet more often than usual or when our poo is looser or more watery. These changes often settle after several days and are usually attributed to ‘food-poisoning or ‘gastroenteritis’. However bowel cancer and large polyps can also cause these symptoms. Any unexplained change in your bowels lasting more than a couple of weeks is worth mentioning to your doctor. It is particularly important to speak with your doctor or to make an appointment to see a specialist if you are also seeing blood in the poo or experiencing tummy pain or weight loss. I talk more about the causes and investigation of looser or more frequent poo here.
  • A sensation of being unable to completely empty the rectum or back-passage (Tenesmus). Tenesmus is the name that doctors use for the sensation of being unable to completely empty the rectum or back-passage. Tenesmus can be caused by a build-up of hard impacted poo, by inflammation of the lining of the rectum but can also be caused by a growth in the rectum such as a polyp or a cancer. If you experience these symptoms it is important to see your doctor or a specialist.
  • Tiredness or low energy levels (caused by anaemia and iron-deficiency). Tiredness is a very common symptom – just ask any GP! – and it is very rare for it to have a sinister cause. However if blood tests show that you have unexplained anaemic (low haemoglobin or blood count) with low iron levels it is important to see a Gastroenterology specialist. Bleeding into the stomach or into the bowels can cause iron-deficiency anaemia – and bowel cancer or large polyps are one possible cause.
  • Unexplained weight loss. All cancers (not just bowel cancers) can cause unexpected weight loss. If you have been losing weight without really trying, it is important to speak to your GP or a specialist.
  • An abdominal mass. This is quite an unusual symptom. Occasionally large cancers – especially in the caecum (on the right lower part of your tummy) – can be felt as a mass or lump within the tummy.
  • Symptoms of bowel obstruction. Advanced bowel cancer can start to cause a blockage in the colon. This can cause symptoms of severe tummy pain, tummy swelling, vomiting and constipation.

How is bowel cancer investigated?

  • Blood tests Blood tests can sometimes give important clues as to the presence of bowel cancer. They can show the presence of anaemia – which might be caused by bleeding. They can also show the presence of liver problems in advanced cancer.

  • Stool tests Providing poo samples can be a bit messy and unpleasant – but a lot of important information can be gained from stool samples. Your poo can be tested for the presence of small traces of blood or haemoglobin (sometimes elevated with large polyps and bowel cancer). You will not be expected to provide a sample there and then in the clinic – you would normally be given a pot for the poo sample in clinic and you will bring it back to the clinic a few days later.

  • Colonoscopy One of the best ways of investigating for possible bowel cancer is to examine the colon with a thin flexible camera. This allows full colour views of the entire lining of your large intestine so abnormal areas such as polyps and cancers can be clearly visualised. The tests also allow biopsies (tiny pieces of tissue) to be taken from any abnormal areas to look at under the microscope. Finally, almost all polyps can be removed during the test – so colonoscopy is not only a diagnostic test but can also treat problems.

    A colonoscopy test typically takes about 15-20 minutes. It is usually performed as a day-case procedure. You will typically be in the hospital for 2 or 3 hours and will not need to stay overnight – although this can sometimes be arranged if necessary.

    Lots of patients have heard ‘horror stories’ about colonoscopy – a friend of a friend who had a bad experience, usually because of pain. While some patients may indeed have had bad experiences, the key is careful explanation, reduction of anxiety, using adequate doses of sedation and painkiller – and keeping the medicines topped up as necessary! By following these rules, I have found that almost all of my patients find colonoscopy to be a much less scary and unpleasant procedure than they had anticipated.

  • Flexible Sigmoidoscopy Depending on your symptoms, it may be necessary to look at only the lower part of the large intestine, rather than the whole colon. A flexible sigmoidoscopy uses much the same equipment as a colonoscopy test but the camera is only passed to the lower part of your colon (usually to the descending colon). The examination is quicker than a colonoscopy and typically takes only 5 minutes.

    There is usually no need to take a strong laxative beforehand – instead you may be given an enema just before the test to clean out poo from the bottom half of the colon. As the test takes only 5 minutes and the camera is not pushed all the way around the colon it is less likely to be painful. You may choose to have sedation for the test – alternatively you may wish to have the procedure without any medication
  • CT scan of the abdomen and CT scan of the colon (CT colonography, virtual colonoscopy) A CT scanner uses X-rays and computers to generate pictures of cross-sectional ‘slices’ through the body. During a CT scan you will lie flat on a couch which slides inside a giant ring (or doughnut). A CT scan is not at all claustrophobic and typically lasts 5-15 minutes. In CT colonography the CT scanner is used to generate detailed pictures of your rectum and colon.

    The test can be used instead of a colonoscopy to detect cancers and polyps in the large intestine. CT colonography is less invasive than a colonoscopy because the test does not involve inserting a camera all the way around the colon –but it does involve exposure to X-rays. It is however generally a less useful test than a colonoscopy as it does not allow biopsies to be taken or polyps to be removed.

How is bowel cancer treated?

Bowel cancer is curable – especially if caught early. The treatment of bowel cancer is coordinated between specialist surgeons (Lower GI or Colorectal surgeons) and cancer specialists (oncologists). Bowel cancer will almost always mean an operation to remove the diseased part of the colon or rectum. People are often worried that they will need a stoma or bag after the operation but this is usually not necessary except for advanced disease or cancer very low in the rectum. Chemotherapy may also be necessary either before or after the operation and an oncologist will be able to talk more about this with you.

What should I do if I have polyps?

As I discussed earlier, certain bowel polyps (adenomas) have a small risk of eventually growing and turning into bowel cancer. Polyps can usually be removed when you have a colonoscopy – and this removes the risk. However if you have had adenoma polyps in your bowel, there is an increased chance that you will grow more in the future. If you have had an adenoma in the bowel it is important that you have a follow-up colonoscopy to make sure that you are not growing more. Depending on how many and how large your polyps were, the repeat colonoscopy should be in either 1, 3 or 5 years after the polyps were found. Your GP or a specialist will be able to advise you further.

What should I do if I have a family history of bowel cancer?

Bowel cancer is unfortunately a common cancer and many families have at least 1 family member who has been affected. Most bowel cancer is due to ‘bad luck’ rather than ‘bad genes’, but there is a small familial risk. Having a single relative who has had bowel cancer probably does not significantly increase your own risk of developing the disease (unless your relative was diagnosed at a young age). However, if you have more than 1 family member who has had bowel cancer (particularly if at least one of these was a mother, father, brother or sister) you should speak to your GP or specialist about whether you should have regular checks to make sure you are not growing polyps or an early bowel cancer.

What is bowel cancer screening?

As I discussed earlier, it is much easier to cure cancer if it is caught early. At present the NHS offers 2 screening programmes for bowel cancer to help detect it at an early stage before it is causing any symptoms. The programmes also help detect and remove large polyps.

In the National Bowel Cancer Screening Programme, everyone between the age of 60-74y of age (50-74y in Scotland) is invited every 2 years to send in stool samples to check for microscopic traces of blood in the poo (faecal occult blood test or FOBt). Those people where the test detects microscopic traces of blood in the poo are invited for a colonoscopy. Although the test can be rather messy and fiddly as 2 samples are needed from each of 3 consecutive poos, the National Bowel Cancer Screening Programme has been shown to improve the detection of early cancers (or large precancerous polyps) and save lives. However, more than two in five people never return their screening test, putting themselves at risk of late diagnosis. Over the course of the next few years a more accurate and less fiddly stool testing method requiring only 1 sample from 1 poo will be introduced across the UK (the ‘faecal immunochemical test’ or FIT test).

The second bowel cancer screening programme, Bowel Scope, is currently being rolled out across the country so may not yet be available in your area. In the Bowel Scope screening programme, everybody at the age of 55y is invited for a flexible sigmoidoscopy. Any polyps found during the test are removed. Although a flexible sigmoidoscopy examines only the lower part of the colon and does not examine the entire colon, the majority of polyps and cancers are found in the lower colon. A flexible sigmoidoscopy is also a quicker and easier test than a colonoscopy.

Bowel cancer screening can also be arranged privately using colonoscopy, CT colongraphy or home stool tests to look for traces of haemoglobin (FIT test – see above) or bowel cancer DNA (Cologuard).

Certain people have an increased risk of developing bowel cancer and more regular screening with colonoscopy is recommended. People with increased risk of developing bowel cancer include people with previous polyps (adenomas) or bowel cancers, people with genetic conditions predisposing to bowel cancer such as Lynch syndrome, people with a strong family history of bowel cancer and people with ulcerative colitis (a chronic inflammatory condition of the colon). You should speak with your GP or a specialist if you think you may be at increased risk of developing bowel cancer.

This website gives more information about bowel cancer screening:

How can I look after my colon and reduce my risk of bowel cancer?

Prevention is always better than cure. The following tips can lower your risk of developing bowel cancer and – hopefully – help you live a long and healthy life:

  • Reduce your weekly intake of processed meat and red meat Eating processed meat (e.g. bacon, sausages, hot dogs, salami, corned beef, beef jerky and ham) increases your risk of developing bowel cancer. Part of the reason is thought to be chemicals that can form during meat processing. Red meat (e.g. beef, lamb and pork) probably also increases the risk. Red meat can be an important source of key nutrients in the diet so moderation rather than complete avoidance of red meat is the key.
  • Cut down on alcohol Even drinking 1 unit of alcohol per day can increase your risk of bowel cancer. Alcohol also increases your risk of breast cancer, mouth cancer, liver cancer and oesophageal (gullet) cancer.
  • Stop smoking Smokers have a 20% higher risk of developing bowel cancer than non-smokers. Smoking also increases your risk of at least 13 other cancers including cancer of the lung, pancreas, mouth and kidneys. Smoking is the most important preventable cause of cancer in the world. It also increases your risk of heart attacks and strokes.
  • Lose weight Obese people have a higher risk of bowel cancer than non-obese people. Obesity also increases your risk of diabetes, heart disease and liver disease.
  • Increase your weekly intake of dietary fibre, fruit, vegetables and whole grains
  • Take regular exercise

Article written by Dr Neil Galletly, Consultant Gastroenterologist, a talkhealth expert on our online clinic on bowel issues & IBS

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Next review: 22 March 2021