Colorectal cancer is cancer that starts in either the colon or the rectum. Colon cancer and rectal cancer have many features in common. Colon and rectal cancers begin in the digestive system, also called the GI system. The digestive system processes food for energy and the last part of it absorbs fluid to form solid waste that then passes from the body. Cancer that starts in the different areas of the GI system may cause different symptoms. But colon cancer and rectal cancer have many things in common. In most cases, colorectal cancers develop slowly over many years. We now know that most of these cancers start as a polyp -- a growth of tissue that starts in the lining and grows into the center of the colon or rectum. This tissue may or may not be cancer. A type of polyp known as an adenoma can become cancer. Removing a polyp early may keep it from becoming cancer. Over 95% of colon and rectal cancers are adenocarcinomas. These are cancers that start in the cells that line the inside of the colon and rectum.
While we do not know the exact cause of most colorectal cancers, there are certain known risk factors.
Age: The chances of having colorectal cancer go up after age 50.
Having had polyps or colorectal cancer before: 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: Inflammatory bowel diseases, like ulcerative colitis and Crohn's disease increase the risk of colon cancer.
Family history of colorectal cancer: If you have close relatives (parents, brothers/sisters, or children) who have had this cancer, your risk might be increased.
Race or ethnic background: Some racial and ethnic groups such as African Americans and Jews of Eastern European descent have a higher colorectal cancer risk.
Diet: A diet that is high in red meats (beef, lamb, or liver) and processed meats (like hot dogs, bologna, and lunch meat) can increase your colorectal cancer risk.
Lack of exercise: Getting more exercise may help reduce your risk.
Overweight: Being very overweight increases a person's risk of having and dying from colorectal cancer. Smoking: Most people know that smoking causes lung cancer, but long-time smokers are more likely than non-smokers to have and die from colorectal cancer.
Alcohol: Heavy use of alcohol has been linked to colorectal cancer.
Diabetes: People with type 2 diabetes have an increased chance of getting colorectal cancer.
Even though we don't know exactly what causes colorectal cancer, there are some steps you can take to reduce your risk. Regular colorectal cancer screening or testing is one of the best ways to help prevent colorectal cancer. Some polyps, or growths, can be found and removed before they have the chance to turn into cancer. Screening can also help find colorectal cancer early, when it is small and more likely to be cured. If you have a strong family history of colorectal polyps or cancer, you should think about getting genetic counseling to help you decide whether genetic testing or earlier screening may be right for you. You can lower your risk of getting colorectal cancer by taking charge of the risk factors that you can control, such as diet and exercise. It is important to eat plenty of fruits, vegetables, and whole-grain foods and to limit your intake of high-fat foods. Getting enough exercise is also important.
Most of these symptoms are more likely to be caused by conditions other than colorectal cancer, such as infection, hemorrhoids, or inflammatory bowel disease. Still, if you have any of these problems, it's important to see your doctor right away so the cause can be found and treated, if needed.
Screening tests are used to look for disease in people who do not have any symptoms. In many cases, these tests can find colorectal cancers at an early stage and greatly improve treatment outcomes. Screening tests can also help prevent some cancers by allowing doctors to find and remove polyps that might become cancer. The tests used to screen for polyps and colorectal cancer can be divided into 2 broad groups:Tests that can find both colorectal polyps and cancer: These tests are done either by looking at the colon using a scope that is put into the rectum, or with special x-ray tests. Polyps found before they become cancer can be removed, so these tests may prevent colorectal cancer. These tests include: