Colorectal cancer affects 1 in 77 men, and 1 in 132 women, making it the second most common male cancer and the third most common cancer among women.
Despite the prevalence of colorectal cancer, early detection plays a crucial role in improving outcomes. According to Dr Aslam Parker, a gastroenterologist at Mediclinic Vergelegen, the good news is that through regular screening, colorectal cancer can often be identified before it even develops, greatly increasing the chances of successful treatment and survival.
Understanding colorectal cancer screening
“A screening is a test we conduct on a patient before they show symptoms,” Dr Parker explains. “In contrast, a diagnostic test is performed when someone has started to show symptoms.” These may include unexplained weight loss, blood in the stool, or bleeding from the rectum.
Colorectal cancer is usually screened using a one- or two-step process. The one-step process involves a colonoscopy, where a trained doctor uses a tube with a camera to look at your entire colon, from start to end. This helps detect any precancerous growths or polyps. The doctor will carefully examine the colon for at least eight minutes. Dr Parker says the procedure is painless, and if no precancerous signs are found, it only needs to be repeated every 10 years.
If the doctor finds any precancerous growths (called polyps) during the colonoscopy, they can remove them immediately. They might still suggest repeating the procedure in 10 years if there’s only a small chance the polyps could turn into cancer. However, if the polyps have a higher risk of developing into cancer, a follow-up may be recommended sooner.
The two-step process, which may involve stool tests or imaging, is less invasive than a colonoscopy. However, Dr Parker warns that patients who choose this method to avoid a colonoscopy may still need one if polyps are found or if the stool tests show any issues.
One option is faecal occult testing or faecal immunochemical testing, both of which check stool samples for hidden blood. These tests should be done every year. Dr Parker emphasises that if the test shows blood, further investigation with a colonoscopy will be needed.
How often should I have a screen for colorectal cancer?
The Cancer Association of South Africa (CANSA) recommends that individuals should start scheduling colonoscopies from age 50, although Dr Parker says in other countries, screening may start from age 45.
If you have a family history of colorectal cancer, especially if a close relative such as a parent has been diagnosed, you may be advised to start screening at an earlier age. In this case, it's recommended to begin screenings 10 years before the age at which your relative was diagnosed. For example, if your parent was diagnosed at 45, you should start colonoscopies at 35.
If you have a genetic condition that increases your risk of cancer, such as familial adenomatous polyposis (a condition where polyps grow in the colon), you’ll need to start screening earlier and follow a stricter screening schedule. Dr Parker explains that people with this condition have a 100% chance of developing colorectal cancer, so early and regular screenings are crucial to catch any potential issues and ensure that cancer hasn’t spread.
People with inflammatory bowel disease (IBD) also have a higher risk of developing colorectal cancer and should start screening eight years after symptoms appear. How often you need screening depends on your risk of developing cancer. For example, if the disease is only in the rectum, you might need a colonoscopy every 10 years, similar to people without IBD. However, if you're at an intermediate risk, you might need screenings every three years, and if you're at high risk, you may need to be screened annually.
Dr Parker explains that a colonoscopy may be recommended if your doctor needs to investigate symptoms like weight loss, diarrhoea, constipation, or bleeding from the rectum. In this case, the colonoscopy isn’t for routine screening, but to help find what's causing the symptoms. For example, bleeding might be caused by diverticular disease.
Colonoscopy should be standard
“Undergoing a colonoscopy or a stool test is no big deal, but it can make a huge difference in your health by catching cancer early,” says Dr Parker.
“Screening is an important part of staying healthy. Just like many people regularly get mammograms or prostate-specific antigen (PSA) tests, we need to get to a point where a colonoscopy is seen as a regular part of taking care of your health.”