Bowel Cancer

Bowel cancer, also called colorectal cancer, is cancer that arises from the lining of the large bowel (colon) or rectum (the lower part of the large bowel). It is the 2nd most common cancer in men and women in Australia, with approximately 15,000 people diagnosed each year.

What is bowel cancer?

Most bowel cancers start with an abnormal growth in the gut called a ‘polyp’. If left unchecked, the polyp can grow and mutate into bowel cancer. Thankfully, these changes occur over a 5-10 year period, allowing for screening and removal of the polyp before becoming cancerous.

There are some factors that can increase the likelihood of colorectal cancer.

-Genetics: people with first- and second-degree relatives with colorectal cancer or polyps are more likely to develop colorectal cancer than those without a family history. Some families have specific genes that can be identified and in identifying other family members at risk for bowel cancer.
-Smoking
-Alcohol – more than 2 drinks per day
-Red meat
-Fatty foods
-Minimal vegetables

Certain diseases like Crohn’s and ulcerative colitis also increase the risk of colorectal cancer and there are specific screening guidelines for these patients.

What are the symptoms of bowel cancer?

During the early stages of polyp growth and transformation into bowel cancer, most people do not experience any symptoms. When symptoms do occur they may include:
abdominal pain
a change in bowel habit (can be diarrhea or constipation)
blood in the stools – can be either red or black depending on the location of the bleeding
unexplained weight loss
recurrent fever/chills
night sweats – the pillow is soaked with sweat in the morning
thinning of the stools – the stools come out pencil thin

If you have any of these symptoms, you should talk to your doctor. A referral to a Gastroenterologist may be necessary.

How do you diagnose bowel cancer?

Bowel cancer is diagnosed during a colonoscopy. A colonoscopy is performed under a light sedation and involves a thin flexible camera being passed through the anus into the large bowel. If a cancer is found, tiny samples (“biopsies”) are taken to confirm the diagnosis.

If a tumor is found on colonoscopy, other testing that we will organize include:

Blood tests – including haemoglobin, iron levels and a tumour marker called CEA.

CT scan of the chest, abdomen, and pelvis is done to look for any spread outside the colon.

How do you treat bowel cancer?

The definitive treatment for colorectal cancer is surgery. Surgery is curative when the cancer has not spread beyond the colon. Radiation therapy is sometimes used to shrink the tumor before surgery. If there is a concern that there may be spread outside the colon, chemotherapy may be recommended. All treatments are individualized and patients are cared for by a multidisciplinary team which includes a Gastroenterologist, Oncologist, and a Colorectal Surgeon.

After being treated for bowel cancer, regular colonoscopies to check for new polyps are recommended. This process is called ‘the surveillance phase’ and will be organized by your specialist.

What is bowel cancer screening?

Colorectal cancer screening is recommended by all Gastroenterology societies worldwide. The goal of regular colorectal cancer screening is to find and remove polyps before they turn into cancer. The different types of colorectal cancer screening are:

Faecal occult blood test (FOBT). This test looks for trace amounts of blood in the stool sample which can be an early warning sign of an advanced polyp or bowel cancer. This is the test used by the National Bowel Cancer Screening Program (NBCSP) in Australia. It is mailed out to all Australian residents aged 50-74 every few years.

A positive result indicates that a trace amount of blood has been detected and that a colonoscopy is needed to determine the source of the blood. After a positive FOBT results the chance of your specialist finding something during a colonoscopy is:
4 out of 10 – nothing found
5 out of 10 – a polyp
1 out of 10 – bowel cancer

It has been shown that participating in the Australian National Bowel Cancer Screening program decreases your risk of developing cancer, as well as increasing your chance of a cure should cancer be identified.

-Colonoscopy: This is the gold standard for bowel cancer screening.  It allows inspection of the entire colon and is the best way to detect both polyps and bowel cancer. In addition to detection, a colonoscopy allows your specialist to take biopsies, remove polyps and control bleeding. It is both a diagnostic and therapeutic tool.  A colonoscopy takes approximately 15-20 minutes and is performed under sedation.  For anyone with symptoms, a positive FOBT test, or a strong family history of colorectal cancer, a colonoscopy is the recommended test.

-CT colonography: This is a test using a CT scanner to image the colon.  A computer-generated reconstruction of the colon is made and the doctor can virtually inspect the colon.  However, it is less accurate than colonoscopy largely due to the inability to interpret small irregularities of the colon.  Full bowel prep is needed to clean out the colon for the CT scan.  If a polyp is seen on the scan, a colonoscopy is organized which requires a second full bowel prep on a separate day.  Finally, there is the concern of radiation exposure especially if screened multiple times is to be done over many years.  For this reason, CT colonography is usually reserved for the few people in whom a colonoscopy is not able to be completed due to technical difficulties.

To find out more about bowel cancer screening or colonoscopy – [make an appointment]

1-Subsite-Specific Dietary Risk Factors for Colorectal Cancer: A Review of Cohort Studies Anette Hjartåker,  Bjarte Aagnes, Trude Eid Robsahm, Hilde Langseth, Freddie Bray,  and Inger Kristin Larsen J Oncol.