What is colon cancer?

The colon is part of the large bowel, which is part of the digestive system. Colon cancer is more common in older people. In the UK, almost 6 in 10 bowel cancer cases (58%) each year are diagnosed in people aged 70 and over.

We have more information about other types of bowel cancer including:

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Symptoms of colon cancer

Some people start by seeing their GP after experiencing symptoms. But there are other ways you may be diagnosed:

  • Having NHS Bowel Screening

    Bowel screening is a way of finding bowel cancer at an early stage before it causes symptoms.

  • Going to hospital with a problem, such as bowel obstruction

    This is when part of the bowel becomes blocked. It may cause symptoms such as tummy pain, nausea and vomiting, and constipation.

If you are worried about colon cancer, we have more information about the signs and symptoms. If you have any symptoms or notice anything that is unusual for you see your GP straight away.

Causes of colon cancer

Doctors do not know the exact causes of colon cancer. But there are risk factors that can increase your chance of developing it.

Having one or more risk factors does not mean you will get colon cancer. Also, having no risk factors does not mean you will not develop colon cancer.

We have more information about the causes and risk factors of bowel cancers.

Diagnosis of colon cancer

If you have symptoms, you usually begin by seeing your GP. If they think that your symptoms could be caused by cancer, you should see a specialist at the hospital within 14 days.

At the hospital you will usually have:

  • Rectal examination

    A rectal examination is when your doctor feels for any lumps or swelling by putting a gloved finger into your back passage (rectum).

  • Blood test

    You usually have a blood test to check for low red blood cells (anaemia) and to check how well your liver and kidneys are working.

You may then have the following tests:

  • Colonoscopy – this is the main test for colon cancer

    A colonoscopy looks at the inside of the whole length of the large bowel using a thin, flexible tube with a tiny camera on the end of it (colonoscope). You may have a sedative to help you feel more relaxed and it usually only takes about an hour.

  • Virtual colonoscopy

    A virtual colonoscopy uses a CT scan to build up a 3D picture of your bowel. You may have this test instead of a colonoscopy, or if the colonoscopy did not give a clear enough picture.

  • Sigmoidoscopy

    A sigmoidoscopy looks at the inside of the rectum and the part of the colon closest to the rectum. It uses a thin tube with a camera on the end. This may be uncomfortable but is not usually painful.

Waiting for test results can be a difficult time, we have more information that can help.

Further tests for colon cancer

If any of your biopsies show that there is cancer in the colon, you will have more tests. These are to find out more about the cancer. The results help your doctors plan your treatment. You may also have some of these tests again during and after treatment:

  • More blood tests

    Your blood may be tested for a protein called carcinoembryonic antigen (CEA). Some people with bowel cancer have higher levels of this protein. Your doctors may check it regularly to see how well your treatment is working.

  • CT scan

    CT (computerised tomography) scan uses x-rays to build a three-dimensional (3D) picture of the inside of the body.

  • MRI (magnetic resonance imaging) scan

    An MRI scan uses magnetism to build up a detailed picture of areas of your body.

  • PET-CT scan

    PET-CT scan is a combination of a CT scan, which takes a series of x-rays to build up a three-dimensional picture, and a positron emission tomography (PET) scan. A PET scan uses low-dose radiation to measure the activity of cells in different parts of the body.

Staging and grading of colon cancer

The results of your tests help your doctors find out more about the size and position of the cancer and whether it has spread. This is called staging.

A doctor decides the grade of the cancer by how the cancer cells look under the microscope. This gives an idea of how quickly the cancer might grow or spread.

Knowing the stage and grade helps your doctors plan the best treatment for you.

Treatment for colon cancer

A team of specialists will meet to discuss the best possible treatment for you. This is called a multidisciplinary team (MDT).

Your cancer doctor or specialist nurse will explain the different treatments and their side effects. They will also talk to you about things to consider when making treatment decisions.

Surgery is the most common treatment for colon cancer. But the treatment you have depends on the stage of the cancer and where it is in the colon. It also depends on your general health and preferences. You can read an overview of treatment options for colon cancer here.

Treatment may include:

  • Surgery

    Surgery is often used to remove cancer or areas affected by the cancer. It may also be used to help control symptoms.

  • Chemotherapy

    Chemotherapy uses anti-cancer drugs to destroy cancer cells. You may have it after surgery or sometimes as your main treatment if the cancer has spread.

  • Targeted therapies

    Targeted therapies interfere with the way cancer cells grow. They may be given on their own or in combination with chemotherapy.

You may have some treatments as part of a clinical trial.

Most people have changes in how their bowel works after treatment for colon cancer. These effects usually improve over time. We have more information about managing bowel changes caused by treatment.

After colon cancer treatment

Follow-up after treatment for colon cancer

The aim of follow-up care is to make sure everything is going well and to find out if you have any concerns. The appointments are usually every few months in the first year.

We have more information on follow-up care after treatment.

Sex life

Colon cancer and its treatment can affect your sex life. Changes may get better over time, but sometimes they are permanent. If you have any problems or are worried about this talk to your doctor or nurse. They can explain what to expect and there are often things that can help.


Some cancer treatments can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor before you start treatment.

Well-being and recovery

Even if you already have a healthy lifestyle, you may choose to make some positive lifestyle changes after treatment.

Making small changes such as eating well and keeping active can improve your health and wellbeing and help your body recover.

How we can help

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