Anyone can get colorectal cancer. Doctors often don't know why it happens, but they know some of the things that make people more likely to get it. These include:
Age. The disease is most common in people older than 50, and the chance of getting colorectal cancer goes up with each decade past age 40. Cancers are very rare in people younger than 40, except those who have a strong family history of the disease.
Polyps. These growths on the inner wall of the colon or rectum aren’t cancer, but they can lead to it. They’re fairly common in people over age 50. One type of polyp, called an adenoma, makes colorectal cancer more likely. Adenomas are the first step toward colon and rectal cancer.
Your health history. If you’ve had colorectal cancer before, you could get it again, especially if you had it the first time before you were 60. The same is true if you’ve had polyps. Also, people with long-term conditions involving colon inflammation, such as ulcerative colitis or Crohn's disease, are more likely to have colorectal cancer.
Family history. The unusual genes in colon cells that allow polyps and cancers to develop can run in your family. So if you have a parent, brother, sister, or child who has had colorectal cancer, you’re more likely to get it. Your risk is higher if the relative was diagnosed before age 45 or if you have lots of family members with colorectal polyps or cancer. If conditions such as familial adenomatous polyposis, MYH-associated polyposis, or hereditary non-polyposis colorectal cancer run in your family, that raises the risk for colon cancer (and other cancers), too.
Diabetes. People with diabetes are more likely to get colorectal cancer.
Race. African Americans are more likely than members of other U.S. racial and ethnic groups to get colorectal cancer.
If you have a combination of these risk factors, you’re much more likely to get polyps or cancer. Talk about your risks with your doctor, and let them know if anything changes. They may be able to suggest ways to lower your chances and tell you when you need to get checked.
Watch for symptoms like rectal bleeding or a change in your bathroom habits. They could mean you need attention beyond screening.