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Bowel cancer (colon and rectal cancer)

12-minute read

Key facts

  • Bowel cancer refers to a cancer anywhere in large bowel, including the rectum and anus.
  • Risk factors for bowel cancer include older age, drinking alcohol, smoking, not doing enough physical activity, family history, as well as some medical conditions.
  • All Australians between the age of 40 and 74 years are invited to bowel cancer screening, but if you have risk factors or symptoms, such as blood in your poo, speak to your doctor.
  • There are many different treatments options for bowel cancer including surgery, radiotherapy and medicines such as chemotherapy.
  • The earlier bowel cancer is detected, the higher the chance of successful treatment.

What is bowel cancer?

Bowel cancer, also known as colorectal cancer, develops when cells in the wall of the large bowel grow in an abnormal and uncontrolled way. Bowel cancer can occur anywhere along the large bowel, which includes the large intestine, rectum and anus.

Bowel cancer usually grows from the inner lining of the bowel (mucosa) or from small non-cancerous growths on the bowel wall (known as polyps) that change into cancer. If untreated, these cancer cells can spread along the wall of the bowel, to lymph nodes and other parts of the body.

Bowel cancer is the second largest cause of cancer deaths in Australia. It affects both males and females and can happen at any age, but it becomes more common as you get older.

Bowel cancer is categorised into stages, depending on the size and invasiveness of the tumour and how far it has spread through the body:

Stage 0
(carcinoma in situ)
There are abnormal cells in your bowel lining that aren’t cancerous, but may become so.
Stage I Cancer cells have spread deeper into your bowel wall (submucosa or muscle).
Stage II Cancer has spread through the muscle of your bowel wall and may have spread to other organs nearby. It may have spread to up to 3 nearby lymph nodes.
Stage III Cancer has spread to lymph nodes and organs nearby.
Stage IV Cancer has spread further to other parts of your body (for example, the lungs or liver).

What are the symptoms of bowel cancer?

Some people do not notice any symptoms, and learn they have cancer by having a routine bowel screening test.

If you do have symptoms, they may include:

If you have any of these symptoms, see your doctor. In particular, bleeding from the rectum should never be ignored.

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

What causes bowel cancer?

It isn't always clear what causes bowel cancer, but there are some factors that can increase your risk.

Some lifestyle factors can increase your risk of bowel cancer:

  • eating too much processed meat (for example, bacon, ham, salami, sausages)
  • eating too much red meat (for example, beef, lamb, pork)
  • drinking alcohol — even low alcohol consumption may be associated with some risk
  • living with overweight or obesity
  • smoking
  • not doing enough physical activity

Other factors may also increase your chances of bowel cancer, including:

Your family history and some genetic mutations may also increase your risk. Up to 1 in 10 cases of bowel cancer are due to rare genetic mutations. These either remove your protection against getting cancer (Lynch Syndrome), or cause hundreds of polyps to grow in your large bowel (familial adenomatous polyposis, MYH-associated polyposis).

What’s your risk?

Check your cancer risk with Cancer Australia’s calculator.

When should I see my doctor?

See your doctor if you have blood in your stool, unexplained changes in your bowel habits, tiredness, abdominal pain or any other symptoms that may indicate bowel cancer.

You should also speak with your doctor if you are concerned about your risk. Your doctor can advise you about which screening options are right for you.

FIND A HEALTH SERVICE — The Service Finder can help you find doctors, pharmacies, hospitals and other health services.

Can I be screened for bowel cancer?

Screening can help you and your doctor find out if you have cancer even before you have symptoms. The earlier bowel cancer is diagnosed, the greater the chance of successful treatment.

The National Bowel Cancer Screening Program (NBCSP) offers free screening to all Australians aged between 50 and 74 years of age. You’ll be invited to have a simple, free test that you can complete at home.

The screening test for bowel cancer is the faecal immunochemical test (FIT or iFOBT). It is designed to reveal non-visible blood in your stool sample which may be caused by a bowel cancer. If the test is negative, you will be invited to do another test in 2 years. If it is positive, your doctor may refer you for further investigations, such as a colonoscopy, to check for bowel cancer.

If you’re younger than 45 or older than 74 years and concerned about your bowel cancer risk, or you have a significant family history of bowel cancer, speak with your doctor about your situation and what tests are appropriate for you.

For more details, call the National Cancer Screening Register on 1800 627 701.

If you have another medical condition that puts you at higher risk of colorectal cancer, a strong family history or symptoms that could be from bowel cancer, screening with iFOBT may not be recommended for you. Your doctor will discuss other tests that can help screen for bowel cancer.

ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.

How is bowel cancer diagnosed?

Tests for bowel cancer

If you are experiencing symptoms or return a positive test from bowel cancer screening, your doctor may carry out or refer you for some tests. Tests that can confirm or rule out bowel cancer, and work out the stage include:

  • a physical examination, which may include a rectal examination
  • blood tests
  • a colonoscopy or sigmoidoscopy, which uses a camera to look inside your colon, rectum and anal canal
  • a biopsy to take a sample of tissue from an area that looks suspicious in your bowel wall, taken at the time of colonoscopy or sigmoidoscopy
  • scans of your bowel, such as a CT or MRI scan, barium enema (a colon x-ray) or

a PET-CT scan to see whether any cancer has spread

How is bowel cancer treated?

There are several different treatment options for bowel cancer, depending on:

  • the cancer’s stage
  • where in the bowel the cancer is
  • your general health
  • your preferences


Polyps and in situ cancers (Stage 0) can often be removed during a colonoscopy.

For more advanced bowel cancer (Stages I to III), surgery usually involves removing the part of the bowel with the cancer, some nearby tissue, and joining the remaining ends of the bowel together. If the 2 ends of the bowel can’t be reconnected, the surgeon will create an opening to the outside of the body, known as a stoma, so that waste can leave the body. This is known as resection with colostomy.


Radiotherapy involves destroying the cancer cells with radiation. It may be combined with bowel surgery. Your doctor may recommend that you have radiotherapy before or after surgery, depending on your circumstances.


Chemotherapy uses medicines to kill cancer cells in the body.

It may be used:

  • to remove cancers that have spread elsewhere in the body (metastasis)
  • before surgery to shrink tumours (neoadjuvant)
  • after surgery (adjuvant) to kill cancer cells that were not removed during the surgery
  • for palliative treatment, if it’s not possible to perform surgery

Other treatment options include targeted therapy and immunotherapy.

Can bowel cancer be prevented?

While there’s no way to prevent bowel cancer completely, several diet and lifestyle choices can lower your bowel cancer risk:

  • Be physically active for at least 30 minutes most days.
  • Reduce alcohol intake to no more than 10 standard drinks or less per week.
  • Eat wholegrains and fibre, such as brown rice, wholemeal bread, vegetables, fruits, beans and nuts.
  • Eat dairy products such as low-fat milk, yoghurt and cheese in your daily diet, at least 2 and a half serves per day.
  • Limit red meat consumption to no more than one serve per day and avoid processed meat altogether.
  • Quit smoking and avoid breathing in tobacco smoke.

Are there complications of bowel cancer?

Possible complications can happen as a result of treatment of bowel cancer.

Possible complications of surgery include:

  • infection of your wound, or an internal infection
  • changes in digestive function (for example, eating, drinking and/or bowel motions)
  • stoma problems

Possible complications of radiotherapy include:

  • early menopause
  • infertility
  • sexual dysfunction
  • pain or changes in your digestive system, especially your rectum

In addition, living with a stoma can be challenging. If you have one, you may need extra support.

In some cases, bowel cancer may recur in the bowel or elsewhere in the body. Secondary cancer may develop in the liver, lungs or elsewhere.

Resources and support

For more information and support, you can access these resources:

  • Call 1800 555 494 or visit Bowel Cancer Australia to connect with a bowel care nurse from Bowel Cancer Australia and ask for advice.
  • Visit the Cancer Council’s website for fact sheets about bowel cancer symptoms, treatment and prevention.
  • Join the Decembeard campaign to help raise awareness for bowel cancer in Australia.
  • Read all about cancer for Aboriginal and/or Torres Strait Islander peoples.
  • Cancer Council South Australia has information in many different community languages
  • General information from NSW Health about cancer is available online in many community languages.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: November 2023

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