Colorectal cancer: frequently asked questions

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The Cancer Association of South Africa (CANSA) shares the most frequently asked questions about colorectal cancer symptoms and screening.

What is colorectal cancer?

Colorectal cancer is a malignant (cancerous) disease in which cells in the colon or rectum grow and multiply out of control. Because the rectum is part of the colon (the large intestine/bowel), cancer of either the colon or rectum (passageway that connects the colon to the anus) is referred to as colorectal cancer. It’s sometimes referred as colon cancer.

Does colon cancer occur suddenly?

It doesn’t just appear suddenly. It usually starts as a small growth on the colon, called a polyp, which rarely causes symptoms. If left alone over many years, polyps can become cancerous. The only way to know whether it’s there, is to look.

What is a polyp?

A colon polyp is a small clump of cells that forms on the lining of the colon. Most colon polyps are harmless. But over time, some colon polyps can develop into cancer, which may be fatal when only found in its later stages. Anyone can develop colon polyps.

What are the symptoms?

Many don’t experience any symptoms early on. Symptoms depend on the size and location of the cancer. Some commonly experienced symptoms include changes in bowel habits and in stool consistency, blood in the stool and abdominal discomfort. You may also experience: anaemia with fatigue, weight loss, narrow stools, or passing excessive amounts of gas.

How common is colorectal cancer?

In SA colorectal cancer is on the increase and more younger men and women are being diagnosed with it. According to the International Agency for Research on Cancer (IARC), colorectal cancer is the third most common cancer worldwide. In 2020, almost 2 million cases were diagnosed. Internationally it’s one of the most common causes of cancer death, leading to almost 1 million deaths per year. This is despite the fact that effective screening techniques exist that could reduce the number of deaths. IARC estimates that the global burden will increase by 56% between 2020 and 2040, to more than 3 million new cases per year. The estimated increase in the number of deaths from the disease is even larger, by 69%, to about 1,6 million deaths worldwide in 2040.

What are the risks factors?

The most common risk factors include: • Genetic factors – Heredity is perhaps one of the strongest risk factors for developing colorectal cancer. It’s estimated that approximately 20% of all cases of colorectal cancer are hereditary. This risk increases if you have a primary relative, such as a parent, sibling, or child who develops colorectal cancer.

• Lack of regular physical activity.
• A diet low in fruit and vegetables.
• A low-fibre diet. • A high-fat diet.
• A diet high in meats (especially processed meats like biltong, bacon, sausages, etc).
• Overweight and obesity.
• Alcohol consumption.
• Tobacco use.

What are the screening options?

Five types of tests are used to screen for colorectal cancer:

Faecal occult blood test (FOBT) is a laboratory test used to check stool samples for hidden (occult) blood. Typically, occult blood is passed in such small amounts that it can be detected only through the chemicals used in a faecal occult blood test. Currently, three types of stool tests are approved to screen for colorectal cancer: guaiac FOBT (gFOBT); faecal immunochemical test (FIT), also known as iFOBT; and multi-targeted stool DNA testing (FIT-DNA).

Sigmoidoscopy is a minimally invasive medical examination of the large intestine from the rectum through to the nearest part of the colon, the sigmoid colon. There are two types: flexible sigmoidoscopy and rigid sigmoidoscopy.

Colonoscopy is the endoscopic examination of the large bowel and the distal part of the small bowel with a camera, or a fibre optic camera on a flexible tube passed through the anus.

Virtual colonoscopy is the use of computerised tomography (CT) scanning or magnetic resonance imaging to produce two- and three-dimensional images of the colon, from the lowest part, the rectum, to the lower end of the small intestine, and to display the images on an electronic display device.

DNA stool test is a test used to screen for colon cancer in people with no symptoms. It also screens for growths of cells (polyps) that could one day become cancer. The stool DNA test looks for DNA changes and small amounts of blood shed into the stool.

How long can I have colorectal cancer without knowing?

Because early stages can go unnoticed for years, screening is important for early detection. It’s generally recommended that individuals at average risk receive a screening test at least every 10 years.

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