Colon Cancer Risk Factors
No one knows the exact causes of colon cancer. Doctors often cannot explain why one person develops this disease and another does not. However, it is clear that colon cancer is not contagious. No one can catch this disease from another person.
Research has shown that people with certain risk factors are more likely than others to develop colon cancer. A risk factor is something that may increase the chance of developing a disease.
Studies have found the following risk factors for colon cancer:
Age over 50: colon cancer is more likely to occur as people get older. More than 90 percent of people with this disease are diagnosed after age 50. The average age at diagnosis is 72.
colon polyps: Polyps are growths on the inner wall of the colon or rectum. They are common in people over age 50. Most polyps are benign (not cancer), but some polyps (adenomas) can become cancer. Finding and removing polyps may reduce the risk of colon cancer.
Family history of colon cancer: Close relatives (parents, brothers, sisters, or children) of a person with a history of colon cancer are somewhat more likely to develop this disease themselves, especially if the relative had the cancer at a young age. If many close relatives have a history of colon cancer, the risk is even greater.
Genetic alterations: Changes in certain genes increase the risk of colon cancer.
Hereditary nonpolyposis colon cancer (HNPCC) is the most common type of inherited (genetic) colon cancer. It accounts for about two percent of all colon cancer cases. It is caused by changes in an HNPCC gene. Most people with an altered HNPCC gene develop colon cancer, and the average age at diagnosis of colon cancer is 44.
Familial adenomatous polyposis (FAP) is a rare, inherited condition in which hundreds of polyps form in the colon and rectum. It is caused by a change in a specific gene called APC. Unless FAP is treated, it usually leads to colon cancer by age 40. FAP accounts for less than one percent of all colon cancer cases.
Family members of people who have HNPCC or FAP can have genetic testing to check for specific genetic changes. For those who have changes in their genes, health care providers may suggest ways to try to reduce the risk of colon cancer, or to improve the detection of this disease. For adults with FAP, the doctor may recommend an operation to remove all or part of the colon and rectum.
Personal history of cancer: A person who has already had colon cancer may develop colon cancer a second time. Also, women with a history of cancer of the ovary, uterus (endometrium), or breast are at a somewhat higher risk of developing colon cancer.
Ulcerative colitis or Crohn's disease: A person who has had a condition that causes inflammation of the colon (such as ulcerative colitis or Crohn's disease) for many years is at increased risk of developing colon cancer.
Diet and Lifestyle: Studies suggest that diets high in red meat and fat (especially animal fat) and low in calcium, folate, and fiber may increase the risk of colon cancer. Also, some studies suggest that people who eat a diet very low in fruits and vegetables may have a higher risk of colon cancer. However, results from diet studies do not always agree, and more research is needed to better understand how diet affects the risk of colon cancer.
Inactivity and obesity have also been linked to higher risk of colon cancer. Studies have shown that daily physical activity can decrease colon cancer risk by as much as 50 percent.
Cigarette smoking: A person who smokes cigarettes may be at increased risk of developing polyps and colon cancer.
Because people who have colon cancer may develop colon cancer a second time, it is important to have checkups. If you have colon cancer, you also may be concerned that your family members may develop the disease. People who think they may be at risk should talk to their doctor.