Colorectal cancer, or colon cancer, is the second leading cause of death from cancer in the US, but it’s also, fortunately, one of the cancers that can be caught early with screening. Fortunately, rates of colon cancer have been falling over the past two decades, but it’s still expected to kill nearly 53,000 people in 2021. Part of the reason is that not everyone who is recommended to get screened does. According to the CDC, about 3 in 10 adults aged 50-75 are not up to date with colon cancer screening, and as many as 21 million adults ages 45-75 have never been screened.

Nearly 94% of new cases of colon cancer occur in adults 45 years old and older, and the US Preventive Services Task Force recommends that people begin undergoing screening starting at age 45, which the American Cancer Society also recommends for people at average risk.

People at average risk include those who don’t have any of the following:

• A family or personal history of colorectal cancer or a personal history of certain types of polyps.

• Personal history of inflammatory bowel diseases, such as Crohn’s or ulcerative colitis.

• A personal history of receiving radiation in the abdominal or pelvic area to treat past cancer.

• A colorectal cancer syndrome, such as familial adenomatous polyposis (FAP) or Lynch Syndrome.

Screening looks for the different types of polyps that cause most colon cancer, including tubular, tubulovillous, and villous adenomas. These polyps take about ten years to turn into cancer, but they’re asymptomatic early on, which shows the importance of screening to identify and remove them before cancer develops.

How often a person gets screened depends on the test they select, and each has advantages and drawbacks. The gold standard for screening is a colonoscopy, though that’s also a test many people put off as long as possible. If someone chooses an alternative screening method, they should know that an abnormal result will require a colonoscopy as soon as possible. To help patients determine the best screening option, below is an overview of the advantages and disadvantages of each type, adapted from ”A practical approach to selecting a colorectal cancer screening test” from the American Academy of PAs.

Colonoscopy

• This is the gold standard because it’s diagnostic and therapeutic, allowing the clinician to see inside the colon and remove lesions. It is recommended every ten years if the results are normal.

• Advantages: It allows visualization of the whole colon in one session and has long screening intervals.

• Disadvantages: It’s invasive and requires bowel preparation (that no one loves), sedation, chaperoning, and time off work. There is a risk of bowel perforation, bleeding, splenic injury, and anesthesia complications. It relies on operator skills to effectively identify adenomas and on bowel preparation for adequate visualization.

Flexible Sigmoidoscopy

• It is recommended every five or ten years with an annual FIT.

• Advantages: It has a lower risk than colonoscopy, limited bowel preparation, and usually doesn’t require sedation.

• Disadvantages: There is no visualization for the proximal colon, only the lower third.

Visual CT Colonography

• It is recommended every five years.

• Advantages: There is a lower risk than colonoscopy, semi-invasive, and it doesn’t require sedation.

• Disadvantages: It requires bowel preparation, flat or small polyps may be missed, and exposes the patient to radiation. It does not allow for polyp removal or biopsies; there can be incidental extracolonic findings.

gFOBT SENSA

• Stool tests are recommended annually.

• Advantages: It is noninvasive, and no bowel preparation is required.

• Disadvantages: It requires three stool samples and adherence (one-time screening sensitivity is low.) It also detects ingested hemoglobin, so patients should avoid red meat and vitamin C for three days before and after collection.

FIT

• Stool tests are recommended annually.

• Advantages: It is noninvasive, no bowel preparation is required, there are no dietary restrictions, and it only requires a single stool sample.

• Disadvantages: It requires adherence because one-time screening sensitivity is low.

FIT-DNA

• A stool test is recommended every three years.

• Advantages: It is noninvasive, requiring no bowel preparation or dietary restrictions.

• Disadvantages: It requires complete stool specimen collection and adherence because one-time screening sensitivity is low.

Colon Cancer Endoscopy

Less widely used, not formally recommended for primary care providers, and often fraught with reimbursement challenges, this test visualizes the colon with a wireless camera inside a pill-sized capsule a patient ingests. It’s only FDA-approved for people with a previous incomplete colonoscopy or those for whom it is inappropriate. It’s not approved for routine screening in those with average risk.

Choosing a Test

The Multi-Society Task Force on Colorectal Cancer, which includes the American Gastroenterological Association, the American College of Gastroenterology, and the ASGE American Society for Gastrointestinal Endoscopy, ranks the tests as Tier 1, 2, or 3. Tier 1, the most highly recommended screens, are colonoscopy and FIT. Tier 2 includes FIT-DNA, CT colonography, and flexible sigmoidoscopy. The colon capsule endoscopy is in Tier 3 and used only for specific indications. Beyond these rankings, patients and clinicians should engage in shared decision-making, considering the patient’s circumstances and preferences, to determine which screening test is best for them.