Bowel cancer | Mate pukupuku i te whēkau

Also known as colon, rectal or colorectal cancer

Bowel cancer (mate pukupuku i te whēkau) is any cancer that starts in the large bowel (colon) or rectum (back passage). When detected early, it can be successfully treated.

On this page, you can find the following information:

What causes bowel cancer?

Cancer occurs when cells within a certain part of the body divide and multiply too rapidly, producing a lump of tissue known as a tumour. In bowel cancer, this occurs in the colon or rectum. 

Bowel cancer often starts as small, non-cancerous polyps that form on the walls of the large intestine (bowel). Over time, some of these polyps may become cancerous.

If the polyps do become cancerous, the cancer cells can spread to the lymph nodes and bloodstream to other parts of the body, most commonly the liver and the lungs.

Risk factors for bowel cancer

Scientists are still unsure what causes cancer to develop in the bowel, but certain factors make you more likely to develop it, including:

  • Increasing age – in New Zealand 90% of people who develop bowel cancer are over the age of 50 years.
  • Family history of bowel cancer – especially if you have a close family member who has been diagnosed with bowel cancer at a young age (under 55 years)
  • Lifestyle factors, such as:
    • a diet high in red and processed meat, and low in fruit and vegetable fibre
    • smoking
    • drinking large amounts of alcohol
    • inactive lifestyle.
  • Having an inflammatory bowel condition, such as ulcerative colitis, for more than 10 years.
  • Having a rare inherited condition, known as polyposis that can lead to bowel cancer. Read more about polyposis from the NZ Familial GI Cancer Service.

What are the symptoms of bowel cancer?

The three main symptoms of bowel cancer are:

  • blood in your bowel motions – this may look like red blood or black bowel motions
  • a change in bowel habits that continues for several weeks, such as diarrhoea, constipation, or feeling that your bowel doesn't empty completely
  • general abdominal discomfort (frequent gas pains, bloating or cramps) that can be confused with indigestion. 

Other signs and symptoms include:

  • unexplained weight loss
  • tiredness
  • anaemia.

Although these symptoms are often caused by other conditions, it is important to check with a doctor without delay.

Take a look at the NHS Choices Bowel cancer symptom checker .

How is bowel cancer diagnosed?

When you see your doctor, they will ask about your symptoms and whether you have a family history of bowel cancer. Your doctor may carry out some or all of the following tests and procedures to check for bowel cancer:

  • rectal and abdominal examination
  • blood tests
  • a test for blood in the bowel motions
  • sigmoidoscopy
  • colonoscopy
  • CT colonography (also known as virtual colonoscopy).

Read more about these diagnostic tests and procedures.

Treatment for bowel cancer

The three main treatments for bowel cancer are surgery, chemotherapy and radiation treatment. Most people will have surgery, while some people receive a combination of treatments. Monoclonal antibodies may also be used if the cancer has spread to other parts of the body.

Treatment choice depends on the size of the cancer, its location and whether it has spread. Your general health and your wishes are also important in the decision making. In some cases you may want to seek a second opinion.

If bowel cancer is detected early enough, there is a good chance it can be removed successfully and stopped from coming back. However, a complete cure is not always possible and the cancer may return. 

If the cancer has spread so far that it can not be removed completely by surgery, then a cure is very unlikely. In these cases, treatment focuses on controlling symptoms and slowing the spread of cancer.

Read more about treatment for bowel cancer.

Can bowel cancer be prevented?

There are some factors that increase your risk of bowel cancer that you cannot change, such as family history and age. However, there are other factors to do with your lifestyle which you can change and by doing so reduce your chance of developing bowel cancer.

Lifestyle factors

There is strong evidence that certain lifestyle factors contribute to our risk of bowel and other cancers. To combat this, it is recommended that you:

  • adopt a healthy diet that includes:
    • less cured and processed meat, such as bacon, sausages and ham
    • less red meat and more fish
    • more fibre from cereals, beans, fruit and vegetables.
  • exercise regularly:
    • for adults, that’s at least 2.5 hours of moderate intensity activity every week. 
  • maintain a healthy weight:
    • you can find out if you are a healthy weight by using the BMI calculator
    • changes to your diet and an increase in your physical activity will help keep your weight under control.
  • quit smoking.
  • cut back on alcohol.

Read more about bowel cancer prevention from Bowel Cancer NZ.

Early detection

Bowel cancer is the second highest cause of death due to cancer in New Zealand. When detected early, it can be successfully treated.

Bowel screening cannot prevent bowel cancer, but it can help the condition be detected earlier. People who are diagnosed with bowel cancer and receive treatment at an early stage, have a 90% chance of long-term survival. If there is a delay in diagnosis and treatment, the cancer can become more advanced and harder to cure.

In New Zealand in 2011, a study was begun to see whether a bowel screening programme should be rolled out nationally. As a result of the successful pilot, from July 2017 a programme is being rolled out around the country, so that by 2020 bowel screening will be available to everyone aged 60 to 74 who is eligible for publicly funded healthcare in New Zealand. Read more about bowel cancer screening.


Emotions and cancer English/Māori Cancer Society, NZ, 2020
Personal stories Bowel Cancer NZ
How we can help Cancer Society, NZ
NZ cancer services – find a hospital/service near you Healthpoint, NZ

Learn more

About bowel cancer Beat Bowel Cancer Aotearoa, NZ
Brief information about bowel cancer Cancer Society, NZ

Credits: Adapted from Cancer Society of NZ information. Reviewed By: Derek Luo, Counties Manukau DHB (5 May 2017)