As its name suggests, colorectal cancer is a type of cancer that affects the colon or rectum. Cancer is the uncontrollable and abnormal growth of cells. It can happen due to a ton of risk factors. You can control or avoid some of these risk factors while you cannot do the same for other risk factors. Screening tests can help to detect colorectal cancer in the early stages, even before the symptoms develop.

Also Read: Prevention of Colorectal Cancer

Colorectal cancer: overview

Abnormal or uncontrollable growth of cells in the colon or rectum can lead to colorectal cancer. These cells can form a mass called a malignant tumour. Colorectal cancer begins with a lesion or growth in the inner lining of the colon or rectum. These lesions may look like polyps, raised or flat in appearance. Notably, this disease occurs mainly in people of age above 50. As per global data, it is the third most common cancer.

Risk factors

As said earlier, this cancer mainly occurs in people aged more than 50. But recently, the number of cases of this disease among younger people has been increasing. We don't know why the number of cases is increasing. We might need more research to clarify this. Major risk factors associated with this cancer are age and certain conditions. Some such conditions are Lynch syndrome, familial adenomatous polyposis, history of inflammatory diseases, etc. Other risk factors are family history of this disease, excessive alcohol consumption, smoking, obesity, being physically inactive, and maybe diet.

Various screening tests

Stool tests:

The presence of blood in the stool can be a sign of colorectal cancer. Stool tests can reveal the presence of blood in the stool. It can detect a very tiny amount of blood unseen by the naked eye. Although, the presence of blood is due to haemorrhoids. There are three types of tests that the doctors usually prescribe:

• gFOBT test: It detects heme using a chemical. Heme is a protein present in the blood. Heme from other sources like intake of red meat can alter the results. So, the people undergoing this test should not have red meat before the test.
• FIT: It detects the presence of haemoglobin proteins. So, the person undergoing this test doesn't have to avoid any kind of food before the test.
• FIT-DNA: This test relies on the presence of haemoglobin and DNA biomarkers. Cells are shed from the lining of the colon and rectum. These cells collect in the stool. This test analyses the DNA present in these cells.

Trials show that gFOBT performed every two years can reduce the death related to colorectal cancer. However recent studies show that FIT works better than gFOBT. When there are no symptoms, FIT-DNA works better than FIT itself. It is more sensitive and can detect any abnormalities. Doctors recommend conducting this test every 3 years.

Colonoscopy

This test utilizes a colonoscope. A colonoscope is a flexible tube with a lens for examining the inner lining of the colon and rectum. It also has a tool to remove the tissues and is inserted through the anus. During this procedure, the air is pumped to expand the colon. Doctors can see the walls of the colon clearly and remove any abnormal growths. Before the colonoscopy, the colon is thoroughly cleaned. Performing colonoscopy can reduce the risk of getting colorectal cancer. Doctors recommend performing colonoscopies regularly.

Virtual colonoscopy

This kind of colonoscopy utilizes X-rays to form a series of images of the colon and rectum from outside the body. A computer can collect these images and analyze the data. These images are detailed and can show any kind of abnormalities and polyps in the colon or rectum. If any kind of abnormalities is present, one may have to go for a standard colonoscopy.

Sigmoidoscopy

In this test, a tube called a sigmoidoscope is used to examine the rectum and the sigmoid colon. Sigmoidoscopy is a tube with a lens and a tool to remove the tissues. Just like the colonoscope, this tube is inserted through the anus into the rectum and sigmoid colon. Air is pumped to expand the colon so the doctors can see the walls and linings. Doctors can remove any growth or abnormalities using this test.

Blood-based DNA testing

It is a blood test to identify the presence of a gene SEPT9. This test can screen people over 50 years old who have not had a colonoscopy. Although, we don't have any evidence that this test can reduce the risk of colorectal cancer.

Also Read: Ayurvedic Wisdom in Colorectal Cancer Care

Double-contrast barium enema

It is another imaging test like a virtual colonoscopy. It uses X-rays to form images after giving the person an enema with a barium solution. Barium solution can form the outline of the colon and rectum. Hence, the images are clearer. Doctors rarely prescribe this test for colorectal cancer. However, people who cannot undergo colonoscopy undergo this test.

Single spectrum gFOBT

Doctors sometimes perform this test on the stool collected during the digital rectal examination. It may be a part of routine physical examinations. This test also has no evidence that it can reduce the risk of colorectal cancer.

What to do in case of any abnormalities?

If doctors find any abnormalities in the blood test, you have to undergo a colonoscopy. If colonoscopy or sigmoidoscopy reveals anything wrong, doctors will recommend a follow-up colonoscopy. A biopsy may be performed. A polypectomy can further find out if it is cancer. On the other hand, if specialists find anything doubtful in the virtual colonoscopy, you have to do a standard colonoscopy.

Summing up

The screening tests can hint at the early warnings. Hence, it can prevent or detect colorectal cancer. You should be aware of all the risk factors and perform screening tests regularly. Recently, researchers have come up with new markers for detecting this cancer. So, the screening tests will improve in the coming years.

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Reference:

1. Medical Advisory Secretariat. Screening methods for early detection of colorectal cancers and polyps: summary of evidence-based analyses. Ont Health Technol Assess Ser. 2009;9(6):1-65. Epub 2009 Sep 1. PMID: 23074536; PMCID: PMC3377498.
2. Bresalier RS, Grady WM, Markowitz SD, Nielsen HJ, Batra SK, Lampe PD. Biomarkers for Early Detection of Colorectal Cancer: The Early Detection Research Network, a Framework for Clinical Translation. Cancer Epidemiol Biomarkers Prev. 2020 Dec;29(12):2431-2440. doi: 10.1158/1055-9965.EPI-20-0234. Epub 2020 Apr 16. PMID: 32299850; PMCID: PMC7572434.