Causes of Rectal Cancer
Rectal 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 in the mid-60s.
Family History of Colon or Rectal Cancer
Close relatives (parents, brothers, sisters, or children) of a person with a history of colon or rectal 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 or rectal cancer, the risk is even greater.
Personal History of Rectal Cancer
A person who has already had rectal cancer may develop rectal cancer a second time. Also, women with a history of cancer of the ovary, uterus, or breast are at a somewhat higher risk of developing rectal cancer.
Polyps are growths on the inner wall of the colon or rectum. They are common in people over age 50. Most polyps are benign (noncancerous), but some polyps (adenomas) can turn into cancer. Finding and removing polyps may reduce the risk of rectal cancer.
Ulcerative Colitis or Crohn's Disease
A person who has had a condition that causes inflammation of the colon or rectum (such as ulcerative colitis or Crohn's disease) for many years is at increased risk of developing rectal cancer.