Most cancers can only be caught early. Colorectal cancer is one of the very few that can often be stopped before it ever begins.
That is because it usually starts as a polyp, a small growth on the lining of the colon that develops slowly over years. During a colonoscopy, a doctor can find these growths and remove them on the spot, which means the cancer never gets the chance to form. This is why screening for this disease is described as prevention, and not simply as detection.
Screening menus have been widening in recent years. Most guidelines still offer a choice between a stool-based test and a direct visual exam, such as a colonoscopy, as the primary screening methods. Two newer options have been added to that list.
The first is an at-home test that checks stool samples for hidden blood and other molecular markers that may indicate the presence of colorectal cancer. These tests are generally recommended every three years. The second is a blood-based screening test that can be done at a doctor's office, intended for patients who decline both a colonoscopy and a stool-based test.
Colonoscopy remains the preferred screening test for colorectal cancer. It is the recommended option for people at increased risk, including those with a family history of colorectal cancer or with genetic or hereditary syndromes, and for anyone whose doctor has a specific reason for concern. Those at average risk may still be advised to have one.
Stool tests do not require the same amount of preparation as a colonoscopy and are widely used. The newer stool tests have evolved in their ability to detect polyps and abnormal cells in samples.
The blood tests are recommended only if a patient refuses a colonoscopy or a stool test. It is important to note that the blood tests are not as sensitive as the other tests for preventing cancer, though the science is advancing to provide more options. And a colonoscopy will still be needed if a stool or blood test returns a positive or abnormal finding.
Ultimately, the best test is the one that gets done. Offering more options can help detect cancer earlier, or prevent it altogether, simply because more people are willing to go through with something.
As for when to start, many guidelines place the starting point somewhere around age 40 to 45 for people at average risk, and continue screening into the seventies. But the right age and the right test depend on personal and family history, so this is a conversation to have with a doctor rather than a number to apply to yourself.
Healthy lifestyle choices can also help reduce the risk of colorectal cancer. This includes at least 30 minutes of physical activity each day, eating a balanced diet rich in fruits and vegetables, and limiting processed foods. Reducing alcohol intake and avoiding smoking and vaping can lower the risk of colorectal and other cancers as well.