Bowel cancer

The bowel is part of the body’s digestive system. It is a tubular organ that connects your stomach to your anus where waste material is excreted. The bowel is made up of three sections, each with their own particular function:

  • The small bowel – absorbs nutrients from food broken down in the stomach
  • The colon – absorbs water
  • The rectum – a storage space for waste material until it is passed from the body

The bowel has a very high rate of cellular turnover; as materials pass through the bowel, cells that line the organ are often sloughed off and end up being excreted with our waste. Our bodies must constantly replace these lining-cells to take up nutrients and water, and to protect our bowel wall.

Bowel cancer is a disease in which malignant (cancerous) cells form a growth in the lining of the large bowel. Bowel cancer can start from within the bowel wall, or from tiny protrusions called ‘polyps’, which are a cluster of cells that form a small growth within our bowel. These polyps are often harmless, benign (non-cancerous) growths, and can be removed to reduce the risk of bowel cancer, but some polyps can become malignant (cancerous) and spread to other parts of our body (metastasis).

Bowel cancer most often affects the colon or rectum, and is often referred to as ‘colorectal’ cancer. Australia has one of the highest rates of bowel cancer in the world, with around 90 Australians losing their lives to bowel cancer every week. The risk of developing bowel cancer before age 85 in Australia is around one in 12, and men have a higher risk than women. Bowel cancer is the second most common cause of cancer-related deaths in Australia, yet it is one of the most curable cancers if detected and treated early.

The causes and symptoms of bowel cancer

It is difficult to pinpoint just one cause of bowel cancer. This disease is a product of age, our genetic makeup, as well as environmental factors, with diet playing the most important role. Bowel cancer can develop without presenting obvious symptoms, and this explains why it is often diagnosed in its later stages, rather than early. Symptoms of bowel cancer include:

  • Unexpected change in bowel movements (diarrhoea, constipation, more/less frequent bowel movements)
  • Blood (either bright red or very dark), or mucus in the stool
  • General discomfort in the abdomen (eg pain, bloating, wind, feeling of fullness, cramps)
  • Fatigue and lethargy (tired and weak) – a symptom of anaemia
  • Weight loss for no known reason
  • Vomiting

A lot of these symptoms are associated with other unrelated conditions, and can often be easily dismissed as an upset stomach. If you do notice any of these symptoms it does not mean that you have bowel cancer, but it is recommended that you visit your doctor to discuss them.

The risk factors of bowel cancer

Factors that increase your likelihood of developing bowel cancer, or having a relapse of bowel cancer are:

  • Age 50 years and over – your risk increases with age
  • A family history of bowel cancer
  • A personal history of cancer in the colon, rectum, ovary, endometrium, or breast
  • An inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis
  • A history of polyps in the bowel
  • Poor diet – low fibre is associated with an increased incidence of bowel cancer
  • Lack of exercise – people who do regular physical exercise decrease their risk

How bowel cancer is diagnosed

Bowel cancer can be detected and diagnosed using tests that examine the colon and rectal tissue, and blood. These tests are not usually part of a routine check up, and should only be undertaken following a doctor’s advice.

Physical examination and history – an exam from your local GP. Giving your doctor your patient and family history is important.

Faecal occult blood test (FOBT) – this test will check faecal matter (stool) for blood. Stool samples are collected by the patient using a kit and sent off to a laboratory for testing. These FOBT kits can be obtained from your local doctor, or from a pharmacy. The Australian
Government is phasing in a National Bowel Cancer Screening Program for certain age groups in the population.

Digital rectal examination – though this may be uncomfortable, it is rarely painful, and will check for lesions in the back passage.

Barium enema – in some instances a liquid that contains barium (a silver-white metallic compound) is inserted into the rectum. This liquid coats the lining of the bowel and a series of x-rays are taken to detect any obstructions or polyps in the bowel.

Colonoscopy – a colonoscope (a thin tube-like instrument with a viewing lens and a light) is inserted through the rectum into the colon to check for polyps or cancer. It may also have a tool attached to take biopsies or cell samples which will be checked under a microscope.
Biopsy – the physical removal of bowel tissue which is then checked under a microscope for signs of abnormality or cancer.

Options for bowel cancer treatment

Treatment options will depend on the stage of the cancer, whether it is a re-occurring cancer, and also on the patient’s general health and wellbeing. The main treatment for bowel cancer is surgery: surgeons remove the section of the bowel where the cancer is located and most commonly are able to join the two ends together during the same operation. Sometimes a stoma is made during the surgery to allow time for the joint between the two ends to heal. A stoma is an opening of the bowel onto the abdominal wall, and bowel movements will pass through the stoma and into a bag. This is usually temporary, although for some patients this is permanent.

Alongside surgery, chemotherapy and/or radiotherapy are nearly always used to help fight the cancer depending on the level of the cancer and the presence or absence of spread (metastasis). All treatments have side effects. Most are temporary, however some can be permanent depending on the treatment. Your doctor will explain all of the risks involved.

Garvan's research into bowel cancer

The Garvan Institute is home to one of the largest cancer research groups in Australia. Apart from bowel cancer, we also conduct research into breast, prostate, ovarian, pancreatic, bladder and lung cancers, among others.

Our bowel cancer research team is focused on understanding how and why cancer develops and how it should be best treated. This involves three main approaches: 1) study of cancer specimens from patients in collaboration with hospitals, 2) analysis of cancer cells grown in cell culture, and 3) study of tumours in the mouse. One of the current projects has involved the discovery of a new biomarker of bowel cancer - a gene that is altered or silenced in the tumours of about 50% of patients.

We have identified new biological functions for this gene, which normally plays a protective role in a healthy colon. Therefore, if this gene is silenced (i.e. defective), a ‘brake’ that normally helps cells maintain their regular function is removed. However, we are also researching the possibility that the presence of this gene defect could be exploited in optimising cancer treatments.

The aim of all Garvan’s research is to create better diagnosis, better individualised treatments, and ultimately, a better prognosis for patients.

This content is provided for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. If you have any concerns or questions about your health, please consult a suitably qualified healthcare professional.

Key statistics

  • 16,398 to be diagnosed in 2019
  • 11% of all new cancer cases in 2019
  • Third most commonly diagnosed cancer in Australia
  • 1 in 14 Australians will be diagnosed by the age of 85

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