Colon cancer is a leading cause of cancer-related deaths. It typically begins as a small growth of tissue called a polyp in the lining of the colon or rectum. While not all polyps become cancerous, most colon cancers start as polyps, making early detection and removal critical.
Fortunately, colon cancer is highly preventable and survivable. Regular screening plays a key role in identifying and removing precancerous polyps and early-stage cancers, when treatment is most effective. In fact, 9 out of 10 people survive when colon cancer is found early.
Without screening, undetected cancers can progress to advanced stages, such as Stage III and IV, which are associated with poorer outcomes. Colorectal cancer is projected to claim 53,000 lives in 2025.
Understanding your colon cancer screening options will allow you to make informed choices alongside your clinician.
When to Begin Screening for Colorectal Cancer
The American Cancer Society now recommends that individuals at average risk begin regular colon cancer screening at age 45, a shift from the previous benchmark of 50. The lowered screening age reflects rising rates of colon cancer in younger adults and historically low screening compliance for older adults.
You may need to start earlier than 45 if you have:
- A personal history of genetic diagnosis that increases risk of cancer, such as Lynch Syndrome or Familial Adenomatous Polyposis
- A family history of colon cancer, especially in a first-degree relative diagnosed before age 60 or if their cancer is linked to a genetic mutation
- A history of Ulcerative Colitis or Crohn’s disease
- Prior radiation to the abdomen or pelvis for cancer treatment
As an example, if your sibling was diagnosed with Stage 1 colon cancer at age 40, you wouldn’t wait until 45 for your first colonoscopy. Instead, you’d start 10 years before their diagnosis—at age 30.
Given how risk factors change one’s initial screening age it is of critical importance for individuals to know their personal and family history when speaking with their clinician about initial screening.
Screening Options for Colon Cancer
1. Colonoscopy
What it is: A procedure that uses a flexible tube with a camera to examine the entire colon. If polyps are found, they can be removed during the procedure. “A colonoscopy is the gold standard and most preferred method because we can examine the entire colon, locate where the early growths (polyps) are, and remove them on the spot. This is what makes a colonoscopy a cancer prevention procedure,” says Dr. Austin Chiang, Gastroenterologist and author of Gut: An Owner’s Guide.
Other details: This procedure requires patients to undergo preparation (e.g. dietary modifications and laxatives) beforehand to clear the colon so that there is adequate visualization. Since it is performed under sedation most people experience little to no discomfort and have no memory of the exam. The entire process usually takes less than an hour.
2. Flexible Sigmoidoscopy
What it is: A flexible sigmoidoscopy examines only part of the colon, called the sigmoid colon, where colorectal cancer is commonly found. “Some prefer this method because it doesn’t require drinking a full bowel prep, but the tradeoff is that most of the colon is left unexamined,” says Chiang.
Other details: Flexible sigmoidoscopy often uses lighter sedation or none at all. Some patients may experience mild cramping during the approximately 20-minute procedure. While less comprehensive than a full colonoscopy, it can be a more convenient option for some.
3. CT Colonography
What it is: A CT scan that produces 3D images of the colon and rectum to identify abnormalities. However, “if any abnormalities are found, a traditional colonoscopy is still required for further evaluation or removal, ” says Chiang.
Other details: It exposes patients to a low dose of radiation and is best at detecting larger polyps (>1cm). Thus smaller polyps may go undetected.
4. Capsule Endoscopy (e.g. Pill Endoscopy)
What it is: A swallowable capsule with a tiny camera that takes thousands of pictures as it travels through the digestive tract. “Capsule endoscopy can be used to visualize the colon only after incomplete or inadequate colonoscopy. Like other non-invasive tests, including CT colonography, no intervention can be performed during the test,” says Chiang.
Other details: Capsule endoscopy is painless and does not require sedation, but preparation is similar to that for a colonoscopy. The images are transported to an external wearable device and the capsule does not need to be returned. This test’s accuracy can vary based on preparation of bowel. It cannot remove polyps.
5. Fecal Immunochemical Test (FIT)
What it is: A stool test that detects hidden (occult) blood in the stool, which may signal cancer. “A FIT test is done annually, and is designed to detect hidden blood coming from the colon. It is a noninvasive colorectal cancer detection test, designed to detect colorectal cancer,” says Dr. Sophie Balzora, Gastroenterologist at NYU.
Other details: FIT does not require any bowel preparation or dietary restrictions, making it a more convenient option. However, it cannot detect precancerous polyps and must be completed annually to remain effective.
6. Guaiac-based Fecal Occult Blood Test
What it is: Similar to FIT but uses a different chemical method to detect blood in the stool. “This has essentially fallen out of favor. There are better screening detection tests available for average-risk individuals,” says Balzora.
Other details: This test may require dietary changes before stool sample collection. It is recommended annually but is less accurate and largely outdated.
7. Stool DNA Test (e.g. Cologuard)
What it is: Stool DNA test combines FIT with a DNA test to detect cancer-related DNA mutations in stool. “It is done every 3 years assuming a negative test. It, too, is designed to detect colorectal cancer, and not the precancerous growths, or polyps, ” says Balzora.
Other details: It requires no dietary restrictions ahead of giving a stool sample. However, positive results necessitate follow-up with a colonoscopy.
How Often to Get Screened for Colon Cancer
Colon cancer screening is not a one time event. It needs to be repeated to monitor for interval change in the colon. However, the frequency of screening is variable. “If someone has many precancerous polyps, even one large polyp (over 1 cm—about the size of a pea), or polyps with certain microscopic features, they are recommended to come in sooner for their next colonoscopy than someone at average risk or with no prior polyps,” says Balzora.
Conclusion
Regular screening for colon cancer is a powerful tool in reducing the incidence and mortality associated with the disease. While the gold standard test is a colonoscopy, the right test for you depends on your risk level, personal preferences, and access to testing. Speak with your healthcare provider to determine the most appropriate option and timing. The most important point is to not delay screening.
