Colorectal cancer – How is it diagnosed?

The approach to begin screening for colorectal cancer depends on your family history. Essentially, people who have a first-degree family member (in direct relation to you by one generation) with a history of colorectal cancer or a family history of colonic polyps may need more frequent or intensive screening techniques.  

The American Cancer Society recommends commencing regular screening from age 45 for those people with an average risk of colorectal cancer.

Currently there are no major trials that have proven exactly what type of screening is best or how frequently screening should be done. So, the recommendations for patients have been extrapolated from multiple studies and differ from country to country.

Common colorectal cancer screening techniques

Faecal occult blood test (FOBT) 

This checks for hidden blood in the stool.

Process: You collect a stool sample at home and drop the specimen off at a laboratory of your choice as an outpatient.

Frequency: Annually.

Pros: Easy and cost-effective.

Cons:

• Some people don’t like handling their own stool.
• Not very accurate.
• Ideally needs a special diet for up to 72 hours before.

Faecal immunochemical test (FIT) 

Similar to FOBT, FIT detects blood in the stool, but uses antibodies to specifically detect human blood, so improving the accuracy of the test. 

Process: You collect a stool sample at home and drop the specimen off at a laboratory of your choice as an outpatient.

Frequency: Annually.

Pros:

• Easy, cost-effective, and accurate.
• No special diet needed.

Cons: Some people don’t like handling their own stool.

Stool DNA Test 

This test detects altered DNA in stool cells, which can indicate the presence of colorectal cancer or precancerous polyps.

Process: You collect a stool sample at home and drop the specimen off at a lab of your choice as an outpatient.

Frequency: Usually performed every three years.

Pros: Easy and accurate.

Cons:

• Expensive.
• Some people don’t like handling their own stool.
• Not available in all countries or with every laboratory in SA.

Colonoscopy

This procedure allows the doctor to directly examine the inside of the entire colon and rectum, using a flexible tube with a camera.

Process: You undergo sedation(so you’re asleep) as the tube is inserted into your rectum and guided through the colon. This is done in hospital.

Frequency: Typically recommended every 10 years unless polyps (growths in the colon that may turn into cancer over time) are found, and then may need to be done more frequently.

Pros:

• Extremely accurate. 
• Any polyps found can be removed at the same time.

Cons:

• Expensive.
• Any procedure with an anaesthetic is associated with risk.
• Not available to everyone due to the cost of the equipment and access to hospitals.

Flexible sigmoidoscopy

Similar to a colonoscopy, but it only examines the lower part, or left-hand side of the colon.

Process: You may not need sedation as the flexible tube is inserted into the rectum and guided through the lower colon.

Frequency:

• Usually recommended every five years, sometimes in combination with a FIT.

Pros:

• Extremely accurate for the area of bowel that is seen.
• Any polyps found can be removed at the same time.

Cons:

• Expensive.
• Not available to everyone due to the cost of the equipment and access to hospitals.
• Only examines one third of the bowel.

Virtual colonoscopy (CT colonography) 

This technique uses a CT scan to create detailed images of the colon and rectum.

Process: You undergo a CT scan after bowel preparation.

Frequency:

• Typically every five years, but recommendations may vary.
• Pros: No sedation is required.
• Low risk to the patient.

Cons:

• Expensive.
• Not available to everyone due to the cost of the equipment and access to hospitals. 
• If any polyps are seen they can’t be removed, and a colonoscopy needs to be done anyway.
• Doesn’t see small polyps.

Based on the findings, various options will be proposed. If the FIT or any stool-based tests return positive, a colonoscopy and possibly a gastroscopy will be recommended. 

During the colonoscopy, if polyps are discovered, they’ll be removed and sent for analysis. Depending on the number and type of polyps found, a follow up colonoscopy may be recommended within a range of one to five years.

If a lesion, ulcer, or growth that might indicate cancer is identified, a biopsy will be performed, and the sample will be analysed. Should the biopsy confirm cancer, the next steps would typically include a CT scan and possibly an MRI to stage the tumour, which will help in determining the appropriate treatment plan.

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