The colon is part of the large bowel, which is part of the digestive system. In the UK, about 41,000 people get cancer in the large bowel each year. We have more information about other types of bowel cancer including:
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Some people may start by seeing their GP because they have symptoms. Symptoms of colon cancer can include blood in your poo (stools), bleeding from the back passage and a change in your normal bowel habit. If you are worried about colon cancer, we have more information about the symptoms.
Other people may be diagnosed by:
Having NHS bowel screening
Going to hospital with a problem, such as bowel obstruction
If you have any symptoms or notice anything that is unusual for you, see your GP straight away.
The exact cause of colorectal cancer (colon or rectal cancer) is unknown. But, things called risk factors can increase the chance of a person developing it. Having one or more risk factors does not mean you will definitely get colon cancer. And if you do not have any risk factors, it does not mean you will not get colon cancer.
If you have symptoms, you will usually begin by seeing your GP, who will examine you. If they think that your symptoms could be caused by cancer, they will refer you to a specialist doctor.
At the hospital
The doctor will ask you about your general health and any previous medical problems you have had. They will also ask whether you have a family history of bowel cancer.
The doctor will examine you and you will usually also have:
You will usually have a blood test to check your level of red blood cells. If you have a low number of red blood cells, this is called anaemia. You will also have blood tests to check whether your liver and kidneys are working normally.
You may then have:
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. The results will help you and your doctor decide on the best treatment for you. Some tests may be repeated during and after treatment. You may have any of the following tests:
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.
MRI (magnetic resonance imaging) scan
A 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.
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.
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. Find out more about treatment options for colon cancer.
Targeted therapy drugs target something in or around a cancer cell that is helping it grow and survive. Targeted therapies are sometimes used to treat bowel cancers (colon or rectal) that have spread to other parts of the body.
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.
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.
You may get anxious between appointments. This is natural. It may help to get support from family, friends or a support organisation.
Macmillan is also here to support you. If you would like to talk, you can:
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.
Below is a sample of the sources used in our colon cancer information. If you would like more information about the sources we use, please contact us at firstname.lastname@example.org
National Institute for Health and Excellence (NICE). Colorectal cancer: diagnosis and management clinical guidelines. Updated December 2014. Available from www.nice.org.uk/guidance/cg131 (accessed October 2019).
Association of Coloproctology of Great Britain & Ireland (ACPGBI). Volume 19. Issue S1. Guidelines for the management of cancer of the colon, rectum and anus. 2017. Available from www.onlinelibrary.wiley.com/toc/14631318/19/S1 (accessed October 2019).
BMJ. Best practice colorectal cancer. Updated 2018. Available from www.bestpractice.bmj.com/topics/en-gb/258 (accessed October 2019).
European Society for Medical Oncology (ESMO). Early colon cancer: ESMO clinical practice guidelines. Published in 2013. Updated 2019. Available from www.esmo.org/Guidelines/Gastrointestinal-Cancers/Early-Colon-Cancer (accessed October 2019).
MA Rodriguez-Bigas, A Grothey et al. Overview of the management of primary colon cancer. Uptodate 2019. Available from www.uptodate.com/contents/overview-of-the-management-of-primary-colon-cancer (accessed October 2019).
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.
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