Bowel cancer

Bowel cancer is also called cancer of the colon, cancer of the rectum, or colorectal cancer. This cancer occurs when the cells in some part of the bowel grow abnormally and form a lump or tumour which has the ability to spread to other parts of the body.

Most bowel cancers are in the large bowel, which is made up of the colon and the rectum. Occasionally the cancer is in the small bowel, but this is quite unusual. Usually bowel cancer starts in the cells of a polyp, a mushroom-like growth that occurs inside the bowel (colon or rectum). Only about 5% of polyps develop into cancer but all but the smallest polyps should be removed to ensure they don't turn into cancer.

In 2008, bowel cancer was the second most common cancer in New Zealand, and the second highest cause of cancer death. Our death rate from bowel cancer is one of the highest in the developed world. In 2008, 2801 people were diagnosed with bowel cancer, and 1280 people died from the disease. It may occur at any age, although 90 percent of cases are in individuals over the age of 50.

Causes and symptoms of bowel cancer

Scientists are still unsure what causes bowel cancer. It often starts as a benign (not cancerous) polyp that turns into cancer over time. People are more likely to develop bowel cancer as they grow older, with the number rising steeply from the age of 50 and it affects more men than women. Scientists believe a diet high in animal fats and low in fruit and vegetable fibre may contribute to the development of bowel cancer.

You are more at risk of developing bowel cancer if:

  • You have a history of a number of family members over two or three generations being affected with bowel cancer
  • You or a close family member have been diagnosed with bowel cancer at a young age
  • There is concern that you and your family may have a genetic bowel cancer syndrome
  • There is a known genetic bowel cancer syndrome in your family
  • You have had extensive inflammatory bowel disease such as ulcerative colitis for more than 10 years.

Common signs and symptoms of bowel cancer may include:

  • A change in bowel habit - i.e. your regular pattern of going to the toilet
  • Diarrhoea, constipation, or feeling that your bowel doesn't empty completely
  • Blood in your bowel motion

Although these symptoms are usually caused by other conditions it is important to get them checked by your primary health care provider or doctor.

Treatment and screening

People who are diagnosed with bowel cancer, and receive treatment when it is at an early stage, have a 90 percent chance of surviving five years. After five years they have the same survival rate as someone who has never had bowel cancer. If there is a delay in diagnosis and treatment, and the cancer spreads regionally, the five year survival rate drops to 70 percent, and then plummets to 10 percent where there is distant spread.

Bowel screening involves people within a certain age range being asked to take a screening test called an immunochemical faecal occult blood test (iFOBT). An iFOBT is used to detect blood in faeces (bowel motions). People with blood in their faeces will be offered a diagnostic colonoscopy, which can detect polyps and cancers if they are present. Polyps can usually be removed during a colonoscopy. 

A four year bowel screening pilot began in 2012 to determine whether a bowel screening programme should be rolled out nationally. As a result of this pilot programme The National Bowel Screening Programme (NBSP) is being rolled out progressively across all District Health Boards.

Almost $78 million has been allocated to get the programme up and running in the first five DHBs and to cover the cost of establishing a National Coordination Centre and four regional centres. The centres became operational late in 2017. Additional funding has also been set aside for an IT system to support the national programme.

The national roll-out

Hutt Valley and Wairarapa District Health Boards (DHBs) began free bowel screening from July 2017 and Waitemata transitioned from the pilot to the national programme in January 2018. Southern is set to follow in April.
Other DHBs will follow in stages with all DHBs around the country expecting to be offering bowel screening by the end of 2021.

Once the programme is fully rolled-out, bowel screening will be offered every two years to men and women aged 60 to 74 who are eligible for publicly funded health care. Once fully implemented it is expected to detect 500-700 cancers a year.
The NBSP is based on a successful six year pilot programme. Information on the pilot is available on the Ministry of Health website.

To find out more about the National Bowel Screening Programme, including who is eligible, how to do the test, and when it will be offered in your DHB area, go to the National Screening Unit website.

For more information on Bowel Screening and the pilot programme visit the Ministry of Health Website.


While no cancer is completely preventable, you may be able to lower your risk of bowel cancer by eating a healthy diet and exercising regularly.

Enjoy a wide variety of nutritious foods:

  • Eat plenty of vegetables, legumes (dried beans, peas or lentils), fruits & cereals (breads, rice, pasta & noodles), preferably wholegrain.
  • Include lean meat, fish and poultry.
  • Include milks, yoghurts and cheeses. Reduced fat varieties should be chosen where possible.
  • Drink plenty of water.

Take care to:

  • Limit saturated fat and moderate total fat intake.
  • Limit your intake of red meat and processed meat.
  • Choose foods low in salt.
  • Limit your alcohol intake if you choose to drink.
  • Consume only moderate amounts of sugars and foods containing added sugars.

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