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What is colorectal cancer screening? 

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While not as widely known as other types of cancer, colorectal cancer is the second leading cause of cancer death in both men and women in Europe, and one of the most diagnosed cancers. Luckily, several screening tests are available for colorectal cancer, enabling the disease to be caught in early stages or prevented before it can occur. In fact, some types of screening can even be done in the comfort of your own home! This article will summarize what colorectal cancer is, which individuals are at risk, and how to screen for it.

What is colorectal cancer?

Colon cancer is a type of cancer that begins in the large intestine or colon and/or rectum. The colon is the largest part of the large intestine and is responsible for removing water and nutrients from food as it passes through your digestive system. The rectum is the last few inches of the large intestine, where digested food passes through before exiting the body as stool. 

Colorectal cancer occurs when the cells of the colon or rectum begin to divide uncontrollably. This growth often begins as a lesion in the tissue, that lines the inside of the colon or rectum. These lesions can present as raised polyps or be flat and/or indented (National Cancer Institute, 2021). Like any growth on your body, not all polyps in the colon or rectum will become cancer. However, certain polyps known as adenomas are more likely to become cancer. 

Why screen for colorectal cancer?

If identified early with screening, the adenomas can be removed before they develop into cancer. Furthermore, screening can help find colorectal cancers in early stages, before symptoms begin. Identifying cancer early improves the chances that it can be cured, meaning screening can be used for colorectal cancer prevention and early detection. 

What tests detect colorectal cancer?

There are several screening tests that can detect abnormal polyps or colorectal cancer before symptoms begin (Centers for Disease Control and Prevention, 2022). Certain screening tests can be performed from home, while others must be done at a clinic, hospital, or doctor’s office. Read on to learn more about the different types of colorectal cancer screening available.

1) Stool tests

There are currently three stool tests available for colorectal cancer screening. These tests primarily look for hidden (occult) blood in the stool. Occult blood in stool can indicate colorectal cancer or polyps, although not all cancers or polyps bleed. The guaiac-based fecal occult blood test (gFOBT) uses the chemical guaiac to detect blood in stool. The fecal immunochemical test (FIT) uses antibodies to detect blood in the stool (Provincial Health Services Authority, 2022). The FIT-DNA test is a FIT test for blood in stool, combined with a test that detects DNA markers for colorectal cancer.

Performing a stool test is easy and sample collection can be done from home. During sample collection, a stick or brush is used to obtain a small amount of stool. Users then return the test kit to the doctor or a lab, where the stool sample is checked for the presence of blood.

While stool tests can be done through your GP, it is now also possible to perform tests entirely from home. Homed-IQ’s Colon Cancer Screening Test is a FIT stool test that includes everything you need to perform a stool sample at home. The sample is then mailed directly to a certified laboratory for analysis. This method of testing avoids visiting a doctor’s office and allows users to test whenever they like.

2) Sigmoidoscopy

Beyond stool tests, doctors can directly examine parts of the colon or rectum to check for signs of cancer or polyps. This method of testing allows the colon to be visually checked for abnormalities beyond occult blood. Sigmoidoscopy tests are performed by a specialist doctor, usually in their office. During this test, the doctor puts a short, thin, flexible, tube into your rectum. The doctor then checks for polyps or cancer inside the rectum and lower third of the colon.

3) Colonoscopy

A colonoscopy is similar to a sigmoidoscopy, except the doctor uses a longer tube to check for polyps or cancer inside the rectum and the entire colon. During the test, the doctor can identify and remove most polyps and some cancers. As the entire colon is examined, colonoscopies are considered to be the most sensitive test for detecting polyps or colorectal cancer. However, this method of screening is also more invasive, as colonoscopies often require anaesthesia and consuming a powerful bowel preparation liquid beforehand. Therefore, colonoscopy is also often used as a follow-up test if anything unusual is found during one of the other less invasive screening tests, like a stool test. 

How often should you be screened for colorectal cancer?

gFOBT and FIT tests are generally performed once a year, while FIT-DNA tests can be performed every three years (Philips, MedlinePlus, 2021). Sigmoidoscopies are recommended every five years, or every ten years, combined with a FIT test every year. Colonoscopies should be repeated every 10 years for people who do not have an increased risk of colorectal cancer.

Who should screen for colorectal cancer?

In the Netherlands, the target age group for colorectal cancer screening is people between the ages of 55 and 75 (RIVM, 2022). In Germany, screening typically begins at age 50, and the US CDC recommends commencing screening at age 45 for adults with average risk (Centers for Disease Control and Prevention, 2022). People at increased risk of colorectal cancer may start screening earlier. This could be individuals with a family history of colorectal cancer or who have certain types of polyps. 

Does a positive FIT test mean cancer? 

A positive FIT or gFOBT test result means that there was blood in your stool at the time of the test. A polyp, pre-cancerous polyp, or cancer in your colon or rectum can cause blood in your stool. However, many other conditions can also cause blood in your stool to occur. Therefore, a positive FIT or gFOBT test result means that more investigation is needed to determine the cause of the bleeding and whether further treatment is needed.

Additional testing for positive stool or sigmoidoscopy tests usually includes a colonoscopy at the discretion of your doctor. If you receive a positive result using a home stool sampling test, take your results to your GP to be connected to appropriate follow-up care.