What causes colorectal cancer?

While we do not know the exact cause of most colorectal cancer, there are certain known risk factors. A risk factor is something that increases a person's chance of getting a disease. Some risk factors, like smoking, can be controlled. Others, such as a person's age, can't be changed. Researchers have found several risk factors that increase a person's chance of getting colorectal cancer.

Risk Factors for Colorectal Cancer

• Age: Your chance of having colorectal cancer goes up after age 50. More than 9 out of 10 people found to have colorectal cancer are older than 50.

• Having had colorectal cancer before: Even if a colorectal cancer has been completely removed, new cancers could start in other areas of your colon and rectum.

• Having a history of polyps: Some types of polyps increase the risk of colorectal cancer, especially if they are large or if there are many of them.

• Having a history of bowel disease: Two diseases called ulcerative colitis and Crohn’s disease increase the risk of colon cancer. In these diseases, the colon is inflamed over a long period of time and there may be ulcers in its lining. If you have either of these, you should start being tested at a young age and have the tests often.

• Family history of colorectal cancer: If you have close relatives who have had this cancer, your risk is increased. This is especially true if the family member got the cancer before age 60. People with a family history of colorectal cancer should talk to their doctors about how often to have screening tests.

• Certain family syndromes: A syndrome is a group of symptoms. For example, in some families, members tend to get a type of syndrome that involves having hundreds of polyps in their colon or rectum. Cancer often develops in one or more of these polyps.
If your doctor tells you that you have a condition that makes you or your family members more likely to get colorectal cancer, you will probably need to begin colon cancer testing at a younger age and you might think about genetic counseling.

• Ethnic background: Jews of Eastern European descent (Ashkenazi Jews) have a higher rate of colon cancer

• Diet: A diet high in fat, especially fat from animal sources, can increase the risk of colorectal cancer

• Lack of exercise: People who are not active have a higher risk of colorectal cancer

• Smoking: Most people know that smoking causes lung cancer, but recent studies show that smokers are 30% to 40% more likely than nonsmokers to die of colorectal cancer. And smoking increases the risk of many other cancers as well.

• Alcohol: Heavy use of alcohol has been linked to colorectal cancer