Learn About Colon Cancer Screening Information Online

Understanding Colon Cancer: What You Should Know

Colon cancer, also called colorectal cancer, starts in the large intestine (colon) or the rectum. According to the American Cancer Society, colon cancer is the third most common cancer diagnosed in both men and women in the United States. In 2023, an estimated 106,970 new cases of colon cancer were diagnosed, with about 46,850 deaths from the disease.

The colon is part of your digestive system. It removes water and nutrients from food and stores waste until you have a bowel movement. When cells in the colon or rectum grow abnormally, they can form growths called polyps. Over time, some polyps can become cancerous. This process usually takes several years, which is why screening is so valuable. Finding and removing polyps before they become cancer can prevent the disease from developing.

Several risk factors increase your chance of developing colon cancer. Age is a significant factor—the risk goes up as you get older. Most colon cancers occur in people over 50. Family history matters too. If close relatives have had colon cancer, your risk is higher. Other risk factors include a personal history of polyps or inflammatory bowel disease (like Crohn's disease or ulcerative colitis), obesity, smoking, heavy alcohol use, and a diet high in red or processed meats.

Many people with colon cancer in early stages have no symptoms. This is one reason screening is important. When symptoms do appear, they might include changes in bowel habits lasting more than a few weeks, blood in the stool, persistent abdominal discomfort, weakness, or unexplained weight loss. However, these symptoms can also be caused by other conditions. That's why talking with a doctor about your symptoms and risk factors is essential.

Takeaway: Colon cancer develops slowly and often has no early symptoms. Understanding your personal risk factors and how screening works is the first step toward making informed decisions about your health.

Who Should Get Screened: Age and Risk Considerations

Screening recommendations have changed over time as research has shown benefits of earlier detection. The American Cancer Society recommends that people at average risk begin colorectal cancer screening at age 45. This is a change from the previous recommendation of age 50. Some organizations, like the U.S. Preventive Services Task Force, also recommend starting at age 45 for average-risk individuals.

If you have risk factors beyond your age, you may need to start screening earlier or be screened more frequently. People with a family history of colon cancer in a first-degree relative (parent, sibling, or child) before age 55 should talk with their doctor about starting screening earlier than age 45, sometimes as early as age 40 or even earlier depending on family history. Those with a personal history of polyps or colon cancer need ongoing screening. People with inflammatory bowel disease may need surveillance starting in their late 20s or 30s, depending on how long they've had the condition and other factors.

Genetic syndromes also affect screening recommendations. Hereditary polyposis syndromes like familial adenomatous polyposis (FAP) and Lynch syndrome (hereditary nonpolyposis colorectal cancer or HNPCC) carry very high risks. People with these conditions need specialized screening plans, often starting much younger and involving colonoscopy more frequently.

For people at average risk with no symptoms or family history, screening typically continues until around age 75 to 85, depending on life expectancy and overall health. After age 85, the benefits of screening generally decrease, and screening is not usually recommended. However, decisions about screening at any age should involve discussion with your healthcare provider about your individual situation.

Takeaway: Your age and risk factors determine when and how often you should consider screening. A conversation with your doctor about your personal and family health history helps create a screening plan that makes sense for you.

Types of Colon Cancer Screening Tests Explained

Several screening methods can detect colon cancer or polyps. Each has different benefits and considerations. Understanding what each test involves helps you have an informed conversation with your healthcare provider.

Colonoscopy is often considered the gold standard for colon cancer screening. During this procedure, a doctor uses a long, flexible tube with a camera (called a colonoscope) to view the entire colon and rectum. If polyps are found, they can be removed during the same procedure. The procedure takes about 30 to 60 minutes. You must prepare by emptying your colon completely using a laxative solution the day before. Colonoscopy can detect polyps of any size and allows for removal and tissue samples. It requires sedation and someone must drive you home. The main drawback is that it requires more preparation and recovery time than some other options. According to the National Cancer Institute, colonoscopy can prevent up to 70% of colorectal cancers.

Flexible sigmoidoscopy is similar to colonoscopy but uses a shorter scope that only examines the lower part of the colon and rectum. The procedure takes about 20 minutes and requires less preparation—usually just an enema. No sedation is typically needed. However, it only views about the lower third of the colon, so cancers or polyps higher up may be missed. It's often recommended every 5 to 10 years, sometimes combined with stool-based tests.

High-sensitivity fecal occult blood tests (FOBT) look for microscopic blood in your stool that's not visible to the naked eye. You collect small samples from multiple bowel movements at home and send them to a lab. This test is simple and requires no preparation, but it's less sensitive than colonoscopy at detecting polyps. Positive results typically require follow-up colonoscopy. It's usually recommended annually.

Fecal immunochemical tests (FIT) are similar to FOBT but use antibodies to detect blood in stool. They are more specific for human blood and less likely to produce false positives from diet. Like FOBT, they require at-home collection and annual screening. Results should be confirmed with colonoscopy if positive.

Stool DNA tests (multi-target stool DNA tests) detect both blood and changes in DNA in stool that may indicate cancer or advanced polyps. You collect an entire bowel movement in a container at home and mail it to a lab. These tests can detect some cancers and larger polyps but may miss smaller polyps. They're typically done every 3 years. One trade-off is cost—these tests may not be covered by all insurance plans.

CT colonography (virtual colonoscopy) uses CT scanning to create images of the colon and rectum. You still need bowel preparation similar to colonoscopy. The procedure takes about 10 to 15 minutes and requires no sedation. However, if polyps are found, you'll still need a colonoscopy to remove them. It's usually recommended every 5 years.

Takeaway: Different screening tests have different advantages. Some focus on finding polyps you can remove, while others detect cancer or blood. Your doctor can discuss which test might fit your health situation and preferences.

How to Prepare for Screening Tests

Preparation depends on which screening test you choose. For tests that require you to see inside the colon (colonoscopy, sigmoidoscopy, or CT colonography), bowel preparation is essential. The colon must be empty and clean so the doctor can see the entire surface clearly.

For colonoscopy, preparation typically starts the day before your procedure. You'll receive specific instructions from your healthcare provider, but generally you'll take a laxative solution that you drink throughout the day. Common preparations include polyethylene glycol solutions (like GoLYTELY or MoviPrep), which you drink in large quantities over a few hours. You'll have several bowel movements as your colon empties. You may also be told to follow a clear liquid diet the day before—this means water, clear broth, apple juice, and similar liquids, but no milk, solid food, or red-colored drinks. The day of the procedure, you'll typically continue with clear liquids until a few hours before the appointment.

You'll need to arrange for someone to drive you home after colonoscopy because of the sedation used. Plan to