Bowel cancer

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Bowel cancer is cancer that starts in your large bowel (colon) or inside your back passage (rectum). It’s also called colon cancer, rectal cancer, and colorectal cancer. Bowel cancer is one of the most common types of cancer in the UK. More than 40,000 people are diagnosed with bowel cancer each year.

About bowel cancer

If you have bowel cancer, cells in your large bowel (colon) or back passage (rectum) start growing out of control. Most bowel cancers (around 7 in 10) are adenocarcinomas that start in the glandular cells of the colon. Around 3 in 10 start in the rectum. They usually develop from small, non-cancerous (benign) growths of tissue called polyps. Polyps can become cancerous (malignant) over time.

Bowel cancer can spread:

  • through the wall of your bowel to the surrounding tissues
  • to nearby lymph nodes
  • to other parts of your body, such as your liver and your lungs

The earlier bowel cancer is diagnosed, the better your chance of surviving it. So it’s important to see a GP if you have symptoms, and to consider using screening tests if you’re offered them.

Image showing the large and small bowels

Causes of bowel cancer

It’s not known exactly what causes bowel cancer. It probably happens because of a mixture of different things.
You can develop bowel cancer at any age. But it’s rare before the age of 50. You’re more likely to get it as you get older. Your risk of developing bowel cancer is also higher if you:

  • have a family history of bowel cancer – you’re more likely to get it if your sibling or one of your parents has it
  • have an inherited bowel condition, such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (HNPCC), also called Lynch syndrome
  • have a long-term bowel condition, such as Crohn's disease or ulcerative colitis
  • have a history of non-cancerous growths (called polyps or adenomas) or previous cancers in your bowel

If you have any of these ‘risk factors’, your doctor may recommend you go for regular bowel cancer screening.

Other things that can increase your risk of bowel cancer include:

If you have any of these risk factors, it doesn’t mean you’ll definitely get bowel cancer – but they increase your chances of developing it. You can also develop bowel cancer without having any of them.

Symptoms of bowel cancer


An image showing the symptoms of bowel cancer
An image showing the symptoms of bowel cancer
An image showing the symptoms of bowel cancer
An image showing the symptoms of bowel cancer

People don’t always get bowel cancer symptoms in the earlier stages. If you do, symptoms of bowel cancer can include the following.

  • Bleeding from your bottom or blood in your poo may be one of the first signs of bowel cancer. The blood can be bright or dark red on the surface or mixed in with the poo. Or you may notice it in the toilet bowl. Occasionally it can make your poo look black, like tar.
  • Changes in your bowel habits. Your poo may be looser (diarrhoea) or you may find it harder to go (constipation). You may feel like you need to go more often or more urgently, or you might feel like you haven’t finished even when you’ve just been.
  • You might feel extremely tired and weak (fatigued). This can be due to anaemia. This means you have a lower-than-normal level of red blood cells.
  • Pain or discomfort in your tummy (abdomen) or back passage (rectum) that doesn’t go away.
  • Losing weight, when you haven’t been trying.

If you have these symptoms, it doesn’t necessarily mean you have bowel cancer – they can also be symptoms of much less serious conditions. These conditions include irritable bowel syndrome or piles (haemorrhoids). But contact your GP if you have these symptoms, especially if they don’t go away and aren’t normal for you. Talk to a GP if you’re worried about blood in your poo too.

Sometimes, bowel cancer can cause a blockage (bowel obstruction). This can cause:

  • sudden cramping pains in your tummy
  • bloating
  • constipation
  • being sick

Seek immediate medical attention if you get these symptoms.

Diagnosis of bowel cancer

Your GP will ask about your symptoms and your medical history. It may help to keep a diary to track your symptoms, which you can share with the GP. The GP will examine you by feeling around your tummy and inside your back passage (rectum) to check for any signs of lumps or swellings.

The GP may give you a blood test to see if you have other health conditions, such as anaemia. The blood test will check your general health too.

If you have symptoms of bowel cancer, your GP may give you an at-home test that checks for hidden blood in your poo. This test is called a faecal immunochemical test (FIT). You may be given this test at your GP appointment to take home, or a test may be sent to you in the post. You collect a tiny sample of your poo in a container. Your GP will tell you what to do with the poo sample. You may need to take it to your GP surgery or the hospital or send it in the post directly to a lab. The poo sample is then checked for blood.

If the FIT test shows there’s blood in your poo (called FIT positive), this doesn’t mean you have bowel cancer. But your GP will refer you to a hospital for further tests. If there isn’t any blood in your poo (called FIT negative), but your GP thinks your symptoms still need further investigation, they’ll refer you to a specialist doctor. This may be a medical consultant who specialises in bowel conditions (colorectal specialist). If your FIT test was negative, but your symptoms continue, change, or get worse, it’s important to go back to your GP.

Your specialist doctor may suggest some of the following tests.

  • A colonoscopy. This is the main investigation method for bowel cancer. This will allow your doctor to look at the lining of your large bowel using a narrow, flexible, tube-like telescopic camera called a colonoscope. Your doctor can also use this to take a small sample of tissue (biopsy), which they’ll send to a lab to look for cancer cells.
  • A sigmoidoscopy. This is similar to a colonoscopy. But it just looks at the inside of your back passage (rectum) and the lower part of your bowel. Your doctor may suggest it as an alternative to colonoscopy.
  • A virtual colonoscopy. This uses a CT scan to create a three-dimensional image of the inside of your bowel. This option is offered in some areas if you aren’t well enough to have a colonoscopy. It’s also known as CT colonography.

If these tests find you have bowel cancer, you’ll need further tests to find the size and position of the cancer, and to check if it has spread. This is called staging and may include CT and MRI scans.

Screening for bowel cancer

If you’re registered with a GP surgery, they’ll invite you for bowel cancer screening every two years. When you’re invited for screening depends on where you live.

  • In England, you’ll be offered bowel cancer screening if you're aged between 50 and 74.
  • In Northern Ireland, you’ll be invited for screening if you’re aged between 60 and 74.
  • In Scotland, screening is offered between the ages of 50 and 74.
  • In Wales, screening is offered between the ages of 50 and 74.

You can also request a test if you're older than 74. Screening is important because it may detect bowel cancer early, before you have symptoms. This is when treatment is likely to be more effective, leading to improved outcomes.

The screening kit is called the faecal immunochemical test (FIT). It’s the same test that your GP may recommend if you have symptoms of bowel cancer. The test is sent to you to do at home. It can detect small amounts of blood in your poo that you may not normally notice. If you have an abnormal screening result, you’ll be offered a colonoscopy.

While bowel cancer screening can help to detect cancer, it isn’t perfect and might not always pick it up. So it’s important to look out for symptoms, even if you’ve had a clear screening result.

Your GP surgery will have information about the bowel cancer screening programme in your area.

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Treatment of bowel cancer

Your treatment and care for bowel cancer will be managed by a multidisciplinary team (MDT) of doctors and other cancer specialists. They’ll discuss what bowel cancer treatment they recommend for you. This will depend on:

  • the size of your tumour (lump of cells)
  • the position of your tumour
  • whether your tumour has spread
  • your general health and fitness

If you find out you have bowel cancer early on, it may be possible to cure it. If you’re diagnosed later and the cancer has spread, the focus of treatment may be on prolonging your life and reducing your symptoms.

If your cancer is advanced, treatment will be guided by the size and location of your tumour, to help determine targeted therapies.

Surgery

If possible, your medical team will aim to remove the cancer with bowel surgery. This may be:

  • keyhole (laparoscopic) surgery – the surgeon will insert tiny instruments into several small cuts in your tummy
  • open surgery – your surgeon will make one large cut in your tummy

Your surgeon will remove the affected part of your large bowel and, if possible, join the two open ends together. Sometimes they may form a stoma to give your bowel a chance to heal. This is where the end of your bowel is brought out to the surface of your tummy. A stoma bag is placed over the stoma to collect the waste from your bowel.

A stoma is usually temporary and can be reversed a few months later in another operation. But sometimes, if a lot of your bowel has been removed, you may need a permanent stoma. Most people won’t need this, but your surgeon will be able to let you know how likely it is for you. If you do need a stoma, a nurse will visit you after your operation to discuss with you how to care for your stoma.

Non-surgical treatments

  • You may have some of the following treatments as well as, or instead of, surgery.
  • Chemotherapy – this uses medicines to kill cancer cells. You might have this before surgery to shrink the tumour (lump of cells) or after surgery to reduce the chance of the cancer coming back. If you’re not able to have surgery, you may have chemotherapy to help slow down the growth of cancer and reduce your symptoms.
  • Radiotherapy – this uses radiation to destroy the cancer cells. You might have this if your cancer is in your rectum, alongside surgery and other treatments.
  • Targeted cancer drugs – these are medicines that can seek out cancer cells and interfere with the way they grow. They’re sometimes used alongside chemotherapy for bowel cancer, especially if the cancer has spread to other parts of your body.

Prevention of bowel cancer

It’s not always possible to prevent bowel cancer. But there are certain changes you can make to your lifestyle to help keep your risk as low as possible.

If you have a condition called Lynch syndrome, your doctor may recommend you take aspirin every day to help prevent bowel cancer. Ask your doctor for more information.

Screening for people at high risk of bowel cancer

If you’re at high risk of bowel cancer, you may need regular screening tests to check for any cancerous changes in your bowel. You’re at greater risk if, for example, you have a strong family history of bowel cancer or a particular health condition such as ulcerative colitis. If any polyps (growths of tissue) or areas of concern are spotted during your screening test, they may be removed to prevent cancer developing. Colon polyps can be removed with a procedure called a colonoscopy . Larger polyps may need to be removed by surgery.

If you think you may have an increased risk of getting bowel cancer, ask a GP about screening.

Bowel cancer is treatable and can usually be cured, especially when it’s diagnosed early on. Surgery to remove part or all of your bowel is the main treatment. You may also be offered chemotherapy, radiotherapy, or both of these. If you have any symptoms of bowel cancer, such as blood in your poo, it’s important to speak to your GP. See our Treatment of bowel cancer section for more information.

You can develop bowel cancer at any age. But it’s most common in people older than 50. You may be more likely to have bowel cancer if it runs in your family, or if you have an inherited bowel condition or a long-term bowel condition, such as Crohn’s disease. See our causes of bowel cancer for more information.

Bowel cancer can be caused by a mixture of different things. Eating lots of processed and red meats, not exercising regularly, and smoking or drinking a lot of alcohol may increase your risk of getting bowel cancer too. See our causes of bowel cancer for more information.

You don’t always get symptoms in the early stages of bowel cancer. But you may notice bleeding from your bottom, blood in your poo, or changes in your bowel habits. You may feel extremely tired and weak and have pain or discomfort in your tummy or bottom that doesn’t go away. See our Symptoms of bowel cancer section for more information.

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