Bowel cancer: symptoms, screening and treatments

Published June 2024 | 6 min read 
Expert contributors Dr Nabila Ansari, colorectal surgeon at Royal Prince Alfred Hospital and Chris O’Brien Lifehouse cancer treatment centre 
Words by Michelle Herbison 

Early signs of bowel cancer aren’t obvious for most people – that’s why bowel cancer screening is essential to ensure the best chance of treatment success. 

As Australia’s fourth most commonly diagnosed cancer, bowel cancer – or colorectal cancer – claims the lives of more than 5,300 people every year.  

But when caught early, bowel cancer treatments can be very successful, with around 90% of stage one and two cases having “excellent survival rates”, according to Dr Nabila Ansari, colorectal surgeon at Royal Prince Alfred Hospital and Chris O’Brien Lifehouse in Sydney.  

“One of the problems is you can go for a long time with bowel cancer and not have any symptoms,” she explains. “But when a stage four cancer is found, only 14% of those people at five years are cancer free.”  

Australia’s National Bowel Cancer Screening Program offers free at-home tests to eligible Australians aged between 45 and 74 – but, says Dr Ansari, not enough people are completing them. 

What is bowel cancer?

In about 90% of bowel cancer cases, a tumour called an adenocarcinoma forms in the large intestine. Bowel adenocarcinomas grow in the glandular tissues that line the bowel and usually begin as small growths called polyps. As Dr Ansari explains, it takes about five years for a polyp to become an early cancer, so ideally these can be detected early and removed.

Like other cancers, bowel cancer is classified by stage at the time of diagnosis, says Dr Ansari.

• Stages 1 and 2 bowel cancers are confined to the bowel wall.
• Stage 3 bowel cancer has spread to local lymph nodes.
• Stage 4 bowel cancer has spread to at least one other area of the body, most commonly the liver, lungs and peritoneum (a membrane that covers the organs in the abdomen).

If bowel cancer spreads to another organ, for example the liver, this is known as secondary or metastatic bowel cancer in the liver (not liver cancer).

Other rarer types of cancer that can affect your bowel include lymphoma and neuroendocrine tumours. Anal cancer is rare but disproportionately affects women. Cancers starting in the small bowel are also rare.

How common is bowel cancer in Australia?

More than 15,300 Australians are diagnosed with bowel cancer every year, with just over half of these cases occurring in men.

While 69 is the average age of diagnosis, one in 20 Australians will be diagnosed with bowel cancer by the age of 85.

“It’s very common, especially if you look at the fact that it affects both genders – unlike breast or prostate cancer,” says Dr Ansari.

Although it mostly affects older people, rates of bowel cancer in people under the age of 50 have recently increased to about 15%, she warns. While survival rates depend significantly on the stage at which the cancer is diagnosed, she adds, with about 90% of patients diagnosed at stage one or two being cancer free after five years.

What are common bowel cancer symptoms?

Although many early-stage bowel cancers go unnoticed, you should speak to your GP if you notice any change in your bowel habits.

Symptoms associated with bowel cancer can include:

• blood in your stools, which could be red, dark brown or black
• loose stools or diarrhoea
• constipation or narrow stools
• pain in the abdominal, anal or rectal areas
• unexplained weight loss
• unexplained fatigue and/or anaemia (low levels of healthy red blood cells).

If you’re experiencing symptoms, those really need to be addressed, Dr Ansari urges. “Bleeding is usually related to haemorrhoids, and changes in your bowel habits or abdominal pain can be from lots of things – for example, inflammatory bowel disease.”

Who is at increased risk of bowel cancer?

In around 30% of cases, family history is one of the risk factors for developing bowel cancer. If you have had a family member diagnosed with it, Dr Ansari highly recommends speaking to your GP about regular screening, which could even include planned colonoscopies in some cases.

Age is also a significant risk factor with most cases occurring in Australians aged 45 and over. Other risk factors include a personal history of colon, rectum, ovary, endometrium or breast cancer, a history of polyps in the colon, or ulcerative colitis or Crohn's disease, and some hereditary conditions.

In terms of reducing this risk, Dr Ansari says having a healthy diet and regular exercise habits can lower your chances of developing the disease. Cured, processed and charred meats have also been associated with bowel cancer risk. Dr Ansari recommends increasing your vegetable intake and preferencing fish.

“Research shows that a lot of bowel cancer is related to what we eat and drink,” says Dr Ansari. “For example, people shouldn’t be eating red meat on a daily basis – aim for two to three times a week – and they shouldn’t be smoking or drinking excessively.”

What do bowel cancer screening tests involve?

Thanks to the national screening program, all eligible Australians aged between 45 and 74 receive a simple at-home bowel cancer test in the mail every two years. If you’re outside of the free testing ages through the National Bowel Cancer Screening Program, you might still be eligible to claim towards the bowel cancer screening kit under your extras cover. A two-month waiting period applies^*. Unfortunately, only 40% of eligible Australians have been completing their bowel cancer screening, despite it being a relatively quick, painless and effective process.

“If we find a cancer early, there are very good outcomes for those patients,” Dr Ansari says.

If any traces of blood are found in your stools, you’ll be invited to have a colonoscopy, which she describes as a “very simple day procedure”. If any polyps are found, these can often be removed on the day. If the colonoscopy result is normal, you don’t need to come back for at least five years.

What are the bowel cancer treatment options?

Bowel cancer treatments differ slightly depending on the exact location of the tumour and how advanced it is but can include the following.

Colorectal surgery

Colorectal surgery to remove the affected section of the bowel and nearby lymph nodes usually involves two to seven days in hospital, with two to three months of recovery time. The bowel can usually be rejoined but some patients may require a temporary colostomy bag.

Chemotherapy

Chemotherapy may be recommended if the cancer has spread outside the bowel to lymph nodes or to other organs.

Radiotherapy

Radiotherapy (also known as radiation therapy) is often used before surgery and may be used in combination with chemotherapy to reduce the size and number of cancer cells.

How can bowel cancer impact your life?

When Belinda first told a doctor about the symptoms she was experiencing, she knew something “wasn’t right”.

Living remotely meant she had to travel 50km to a Royal Flying Doctor Service (RFDS) once-a-week clinic to seek a diagnosis. Luckily, she did, as the RFDS doctor immediately sent her for a colonoscopy in Broken Hill and she made the 400km five-hour drive that same day.

Within half an hour of the procedure, a senior surgeon gave her some devastating news.

“He came into my room and said, ‘I am really sorry to tell you that you have a tumour so big it’s blocking your bowel’,” she recalls.

That was the start of many years of chemotherapy, doctor and oncologist appointments, CT scans and regular blood tests.

But she’s pleased to share she’s since received the all-clear.

“My life is mine again,” she says. “Having the RFDS there that day really got the ball rolling and then the aftercare that came with that. The doctor responded in a magnificent manner.”

Do you need to see a GP?

Chat to your GP about any abnormal symptoms or risk factors. Through our partnership with GP2U, all HCF members with health cover can access a standard online video GP consultation (up to 10 minutes) for a fee of $50. See hcf.com.au/gp2u for more information.

And if you’d like a second opinion, we connect eligible members to a network of independent, Australia-based medical specialists for a free second opinion on a health condition you’re worried about^{^}. Eligible members have the chance to ask questions so you can confidently make the best decision for your health.