There are different causes for cancer in different individuals. Some cancers may be caused by a combination of mechanisms, such as exposure to environmental or dietary factors, several genes working together to contribute to cancer formation, or even by chance alone.
Some cancers seem to run in families. For instance, some families have multiple members affected with the same types of cancers (like breast and ovarian cancer or colon and uterine) throughout the generations. Members of these types of families seem to have a hereditary risk of developing cancer. Someone with a hereditary risk of developing cancer is at-risk because of a gene mutation that is passed from generation-to-generation.
While most cancers are NOT due to an inherited tendency, about 10% to 15% are caused by a genetic susceptibility passed through the family. Learning whether a hereditary susceptibility is contributing to a personal and/or family history of cancer can help people affected with cancer as well as their relatives. Genetic counseling and genetic testing may assist in medical decision making for people with cancer and can clarify cancer risks to relatives. In some cases, siblings, children, and other relatives may be reassured that they have not inherited a familial tendency and therefore do not require intensive screening or preventative surgery.
When Should One Suspect a Cancer May Be Hereditary?
A good way to determine whether a cancer is caused by a hereditary tendency is to record the details about cancers, tumors, or growths in your family. Be sure to include the age at which each cancer diagnosis was made and where the cancer started. It is necessary to inquire about cancers occurring in both your father’s and your mother’s families. Usually cancer occurs sporadically (i.e., by chance) in people who are older or who have personal risk factors related to specific cancers (e.g. smoking and lung cancer). Therefore, it is important to note lifestyle traits as well.
When a cancer-causing gene (hereditary cancer) is present in a family one may see:
- Cancer diagnosed at an earlier age than expected for that cancer type (e.g. under age 50 for breast, ovarian or colon and under age 55 for prostate cancer)
- Multiple family members (blood relatives) with cancer on the same side of the family
- Certain related cancers (e.g., breast + ovary or colon + uterus)
- An individual with two or more primary tumors (e.g. bilateral breast cancer, two separate cancers in the same breast or breast AND ovarian cancer)
- Rare tumor types (e.g. male breast cancer, medullary breast cancer, fallopian tube cancer, primary peritoneal cancer, pheochromocytoma)
- Specific ancestry (for example Ashkenazi Jews (from Central and/or Eastern Europe) have an increased frequency (1/40) of carrying a mutation in BRCA1 or BRCA2, one of two genes that predispose the hereditary breast, ovarian and prostate cancer). Common mutations are also found in families from the Netherlands, Iceland, and Sweden
These family history features are only guidelines for assessing the risk for hereditary cancers. When these factors combine in a pattern that is recognizable to a genetics specialist, the pattern may indicate a risk for hereditary cancer. Breast, ovarian and colon cancers are the most common types of cancer that have been linked to specific genes.