What is bowel cancer?

Bowel cancer, also known as colorectal cancer, develops from the inner lining of the bowel and is usually preceded by growths called polyps, which may become invasive cancer if undetected. Depending on where the cancer begins, bowel cancer may be called colon or rectal cancer. 

It is estimated that more than 15,300 people were diagnosed with bowel cancer in 2023. The average age at diagnosis is 69 years old. 

Bowel cancer is the fourth most commonly diagnosed cancer , and it is estimated that one in 20 people will be diagnosed by the time they are 85.

About 90 per cent of bowel cancers are adenocarcinomas, which start in the glandular tissues lining the bowel. Other less common types of cancer can also affect the bowel, including lymphomas and neuroendocrine tumours. 
 
Cancer can also start in the small bowel but this is a rare cancer. 

People aged 50-74 are sent a bowel screening test every two years as part of the National Bowel Cancer screen program. Learn more at bowelcancer.org.au  


Bowel cancer signs and symptoms

Symptoms of bowel cancer include:

  • change in bowel habit including diarrhoea, constipation or the feeling of incomplete emptying

  • a change in the appearance or consistency of bowel movements such as thin bowel stools

  • blood in the stools

  • abdominal pain, bloating or cramping

  • anal or rectal pain

  • a lump in the anus or rectum

  • weight loss

  • unexplained fatigue

  • tiredness and/or anaemia (pale complexion, weakness and breathlessness) 

  • blood in the urine or passing urine frequently or during the night, change in urine colour – dark, rusty or brown.


Causes of bowel cancer

Some factors that increase your risk of bowel cancer include:

  • a diet low in fibre
  • high red meat consumption, especially processed meats
  • being overweight or obese
  • alcohol consumption
  • smoking tobacco
  • inherited genetic risk and family history
  • inflammatory bowel disease such as Crohn’s disease
  • polyps
  • having a previous diagnosis of bowel cancer.

Diagnosis of bowel cancer

A number of tests are used to diagnose bowel cancer. Initially, your doctor will give you a physical examination to feel if you have any abdominal swelling. Your doctor will also give you a digital rectal examination to check for any lumps or swelling in the rectum or anus.

Blood tests

You may have a blood test to see if there are any signs that you are losing blood in your stools. It can also check your red blood cell count as low red blood cells are common in people with bowel cancer.

Immunochemical faecal occult blood test (iFOBT)

You may have an iFOBT (often referred to as FOBT) depending on your symptoms. The test may be used if you have abdominal pain, changes to their bowel habits, unexplained weight loss, or anaemia. It is not recommended if you are bleeding from the rectum.

With the iFOBT, you will take a sample of your stools at home. The sample is examined under a microscope for traces of blood which could be a sign of polyps, cancer, or another bowel condition. It does not diagnose cancer but if blood is detected, your doctor will usually recommend a colonoscopy.

If you’re aged 50-74 you’ll receive a iFOBT test (also known as a bowel screening test) as part of the National Bowel Cancer Screening Program.  

Colonoscopy

The best test for bowel cancer is a colonscopy, which examines the length of the large bowel. Air is pumped into the colon through a flexible tube that is inserted into the anus. A camera on the end of the tube allows your doctor to look for abnormal tissue that is removed for further examination.

Flexible sigmoidoscopy

Flexible sigmoidoscopy is used to examine the rectum and left side of the lower colon. Any unusual tissue can be removed for further examination.

MRI

An MRI scan produces detailed cross-sectional pictures of the body and can show the extent of any tumours.

CT scan

CT scans produce three-dimensional pictures of several organs at the same time and can be used to examine the bowel.

PET scan

In a positron emission tomography (PET) scan, a small amount of radioactive glucose is injected into the body. When scanned, cancer cells will appear brighter.

After a diagnosis of bowel cancer  

After finding out you have bowel cancer, you may feel shocked, upset, anxious or confused. These are normal responses. A diagnosis of bowel cancer affects each person differently. For most it will be a difficult time, however, some people manage to continue with their normal daily activities.  


Treatment for bowel cancer

Treatment for early bowel cancer

Surgery

The main treatment for early bowel cancer is surgery. The most common surgery for cancer that begins in the colon is a colectomy. The type of colectomy performed will depend on whether all or part of the colon needs to be removed.

Radiation therapy (radiotherapy)

Radiation therapy (radiotherapy) is often used before surgery for locally advanced rectal cancer and may be used in combination with chemotherapy to reduce the number and size of cancer cells.

Adjuvant treatment

Chemotherapy may be recommended after surgery for rectal or colon cancer. This aims to reduce the risk of the cancer returning.

Palliative care

In some cases of bowel cancer, your medical team may talk to you about palliative care. Palliative care aims to improve your quality of life by alleviating symptoms of cancer, without aiming to cure it.

As well as slowing the spread of bowel cancer, palliative treatment can relieve pain and help manage other symptoms. Treatment may include radiotherapy, chemotherapy, or other drug therapies.

Treatment for advanced bowel cancer

Systemic treatment

Systemic treatment for advanced bowel cancer uses drugs that move through the bloodstream to reach cancer cells throughout the body. Systemic treatment can include chemotherapy and targeted therapies.

Surgery

You may be offered surgery to remove small secondary cancers if the cancer has spread to other areas of the body.

Side effects  

Treatment for bowel cancer and even the cancer itself, can cause side effects. The types and severity of any side effects you may experience will depend on the type of treatment you have and may vary from person to person. Most side effects are temporary and can be prevented, reduced or managed.    

Some of the side effects you may experience include:   

  • fatigue   
  • nausea and vomiting   
  • hair loss
  • being more prone to infections 
  • changes to bowel habits such as diarrhoea, constipation, incontinence or small amounts of bleeding from the anus 
  • mouth problems
  • changes in appetite, taste and smell
  • high blood pressure 
  • changes to memory and thinking
  • changes to fertility and sexual function. 

Talk to your health care team about any changes you experience during and after treatment.  

Treatment Team

Depending on your treatment, your treatment team may consist of a number of different health professionals, such as:
  • GP (General Practitioner) - looks after your general health and works with your specialists to coordinate treatment.
  • Colorectal surgeon - diagnoses bowel cancer and performs bowel surgery.
  • Gastroenterologist - specialises in diseases of the digestive system.
  • Medical oncologist - prescribes and coordinates the course of chemotherapy.
  • Radiation oncologist - prescribes and coordinates radiation therapy treatment.
  • Cancer nurse - assists with treatment and provides information and support throughout your treatment.
  • Dietitian - recommends an eating plan to follow while you are in treatment and recovery.
  • Other allied health professionals - such as social workers, pharmacists, and counsellors.

Screening for bowel cancer

Bowel cancer can begin without noticeable symptoms. Bowel screening can spot the early signs of bowel cancer - when we find bowel cancer early, successful treatment is more likely. 

If you’re between the age of 50 and 74, as a part of the National Bowel Cancer Screening Program, you will receive a free at-home bowel screening test every two years. 

Your screening test is called a faecal occult blood test (FOBT). It looks for traces of blood in the poo which are invisible to the human eye and could be a sign of bowel cancer. 


Preventing bowel cancer

The risk of bowel cancer can be reduced by a healthy diet with plenty of fresh fruit and vegetables, limiting consumption of red meat, avoiding processed meats, not smoking, limiting alcohol consumption, being physically active, and maintaining a healthy body weight.


Prognosis for bowel cancer

Prognosis refers to the expected outcome of a disease. It is not possible for any doctor to predict the exact course of the disease. An individual's prognosis depends on the type and stage of cancer, as well as their age and general health at the time of diagnosis. This information will also help your doctor to advise on the best treatment options. 

Generally, the earlier bowel cancer is diagnosed, the better the outcomes.