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Genetics

There are many factors that play a role in determining an individual’s cancer risk. Family history is one of them.

Some cancers develop as a result of hereditary factors that occur in families. These cancers are linked to abnormal changes (mutations) in the genetic structure of the body’s cells that are passed from generation to generation. People with these mutations have a higher risk of developing cancer.

Just because a person has a relative who had cancer, it does not mean that cancer is hereditary. About 5 percent to 10 percent of all cancers are considered hereditary. Only a small proportion of some of the most common types of cancer – such as colon and breast cancer – occur as a result of hereditary factors. For other cancers, genetics does not appear to play a strong role in disease development.

Families may have hereditary cancer if there are multiple people in the family with cancer, including more than one generation of family members with the disease. In addition, people diagnosed at a young age are more likely to have hereditary cancer. Some types of hereditary cancer are more common among certain ethnic groups.

People with a strong family history of cancer may want to consider undergoing clinical genetics assessment with a genetic counselor or genetics physician. These professionals typically help patients document their family medical history and collect available medical records of family members with cancer. If a cancer risk appears to be hereditary, they may recommend genetic testing to identify specific gene alterations, typically performed using a blood sample.

Even if an individual is found to carry an altered gene, genetic testing cannot determine if cancer is present or when it may develop. It can only confirm an inherited tendency for the disease. However, results can help patients make some medical decisions, such as determining the best plan for cancer screening or whether to pursue preventive therapy.

For more information about hereditary cancer and Siteman Cancer Center’s hereditary cancer program, click on the links below.