Colorectal Cancer Screening

Colorectal cancer (CRC), referred to as rectal or colon cancer, is one of the most common and deadly forms of cancer globally. However, early detection and prompt treatment can significantly increase survival chances.

CRC screening plays a vital role in identifying this cancer in its initial stages when treatment is most effective.

Understanding Colorectal Cancers

It is important to first understand CRC and associated health implications. Colorectal cancer refers to the abnormal growth of cells in the colon or rectum that multiply uncontrollably in an uncoordinated manner to form a tumor. 

The colon and the rectum are components of the gastrointestinal (GI) system that are responsible for waste processing and elimination from the human body. 

CRCs usually appear as raised polyps, a small growth on the inner lining of the colon or the rectum. With time, a few polyps can become cancerous. Less commonly, CRC lesions appear slightly indented or flat.  Raised lesions may either be attached to the inner surface of the colon or rectum by a stalk (pedunculated polyps) or grow on the surface with no stalk (sessile polyps). 

Usually, colorectal polyps are detected among individuals aged above 50 years. Colorectal cancers are usually asymptomatic in the initial stage, and therefore, hard to detect without proper screening. However, with disease progression, symptoms may develop such as  

• Alterations in bowel habits
• Pain in the abdomen
• Rectal bleeding
• Unexplained loss of weight

These symptoms often indicate that the tumor has advanced, underscoring the critical need for early detection via screening.

Importance of colorectal cancer screening

CRC screening is important for multiple reasons which include:

• Early detection: The primary aim of screening is to identify cancer in the initial and treatable stage. Early diagnosis can increase the chances of treatment success and therefore increase overall survival.
• Prevention: Screening techniques such as colonoscopies can prevent cancer by eliminating precancerous polyps before they turn cancerous. This cancer-prevention dimension of screening can decrease the incidence of colorectal cancers.
• Decreasing mortality: CRC is the third major cause of death from cancer in the United States (US). Regular screening can reduce mortality rates by detecting the tumor before it metastasizes or spreads to other parts of the body. CRC Screening enables the identification of individuals with pre-symptomatic neoplastic (tumor-like) lesions.
• Cost-effectiveness: In the long term, colorectal cancer screening is cost-effective. Treating early-stage cancers is less invasive and less expensive than treating advanced cancers, for which more expensive and extensive therapies may be required.

Screening methods available for colorectal cancers

Various methods are available to screen for colorectal cancers which include:

1. Colonoscopy: Colonoscopy is considered the gold standard for colorectal cancer screening. It involves inserting a flexible tube with a camera into the colon to examine its lining and eradicate polyps while the individual is sedated. Colonoscopies are recommended every 10 years for those at average risk of colorectal cancers. Research has indicated that colonoscopies can prevent over 60% of CRC-related deaths.

2. Fetal Immunochemical Test (FIT) and fecal occult blood test (FOBT): These tests are non-invasive ways to detect occult (hidden) blood in stools, which can indicate colorectal cancer, and are usually performed annually. FBOT uses guaiac whereas FIT uses antibodies to detect blood in the stool.

However, blood may be found in the feces due to other causes, including bleeding in the stomach or upper GI tract, and eating foods such as rare meat. These tests have reduced CRC-related mortality, around 30% if conducted annually and 18% if conducted every alternate year.

3. Flexible Sigmoidoscopy: This procedure is similar to a colonoscopy but only examines the lower region of the colon. The upper part of the colon, the ascending and transverse colon cannot be examined by this method. Flexible Sigmoidoscopy may be recommended every five years. Sigmoidoscopy screening can decrease death from CRC by 59%.

4. CT Colonography (or Virtual Colonoscopy): This involves a computed tomography (CT) scan to generate detailed pictures of the colon and is usually performed every five years. CT colonography could be a substitute for individuals who cannot undergo standard colonoscopy due to the risk of anesthesia, or if an individual has colon blockage, preventing full examination.

5. Double-contrast barium enema (DCBE): For individuals who cannot undergo colonoscopy, an enema containing barium is provided, which makes the colon and rectum stand out on x-rays. Several X-rays are then obtained of the colon and rectum. A barium enema has lower chances of detecting premalignant polyps compared to colonoscopy, CT colonography, or sigmoidoscopy.

6. Stool DNA Testing (e.g., Cologuard): The test combines the detection of deoxyribonucleic acid (DNA) changes and blood in stools. Stool DNA tests are usually conducted every three years.

Why should you consider getting screened?

According to the American Cancer Society (ACS), people at average risk of colorectal cancer should commence regular screening at the age of 45. However, high-risk individuals may require earlier screening and testing.

CRC risk factors include:

• Older age
• Personal history of adenomatous polyps or CRC.
• Personal history of chronic inflammatory bowel disease (IBD)
• History of colorectal cancers or polyps in first-degree relatives (parent/sibling/child), especially in those aged below 60 years.
• Family history of hereditary CRC syndromes, such as Lynch syndrome, familial adenomatous polyposis (FAP)
• Other risk factors include excessive alcohol intake, physical inactivity, and cigarette smoking

How can I reduce my colorectal cancer risk?

In addition to CRC screening, you can lower CRC risk with lifestyle changes as follows:

• Physical exercise: Research has indicated that regular exercise can decrease CRC risk by 24%. Experts advocate 30 to 60 minutes of exercise (including walking the dog, household chores, climbing stairs) on most days of the week.
• Limit alcohol intake: Three or more drinks of alcohol daily increases CRC risk by 41%.
• Quit smoking: Studies have reported that smokers have an 18% higher CRC risk than non-smokers.
• Weight maintenance: Obese women reportedly have 45% higher risks of CRC incidence and mortality than healthy women.

Final thoughts

Colorectal cancers are formidable foes but can be defeated by prompt detection and timely interventions. CRC screening is an important tool, offering the potential to identify the cancer before it spreads and affects other parts of the human body.

Do not wait for symptoms to begin, consult healthcare professionals regarding the most suitable screening technique for you, and take proactive steps towards better overall health and longer, cancer-free lives. 

Colorectal cancer screening could be a lifesaving step towards early detection.