In the United States, a woman has a 1.8% chance of developing ovarian cancer in her lifetime. A woman who has a first degree relative with ovarian cancer (such as her mother or sister) is believed to have a 4-7% lifetime chance of developing ovarian cancer. In families where the pattern of ovarian, breast, and other cancers suggests the cancers are inherited, a woman’s chance of developing ovarian cancer may be as high as 45%.

Although many women have a family history of ovarian and/or breast cancer, only about 5-10% of ovarian cancers are thought to be the result of an inherited cancer susceptibility genes. A family history of ovarian and/or breast cancer may or may not indicate that one has inherited an increased likelihood of developing cancer. Most cases of ovarian cancer are sporadic, meaning they occur in women who do not have a family history of ovarian cancer. Taking a detailed, three-generation family history, or pedigree, is an essential element in the assessment of a woman’s chances of developing ovarian and other cancers.

More frequent evidence of a hereditary susceptibility to cancer within a family includes:

• Two or more women with ovarian and/or breast cancer, especially if the diagnoses occur pre-menopausally
• A woman who has had separate diagnoses of breast and ovarian cancer
• A woman who has had breast cancer in both breasts A man with breast cancer in addition to a female relative with breast or ovarian cancer
• A woman with ovarian cancer at any age who is of Ashkenazi Jewish ancestry.

To date, two main susceptibility genes for breast and ovarian cancer have been identified: BRCA1 and BRCA2. Everyone carries two copies of each of these genes. If a woman inherits an alteration, or mutation, in one of her BRCA1 or BRCA2 genes from either of her parents, her chances of developing ovarian and breast cancer are significantly higher than that of the general population. Siblings and children of an individual known to carry a BRCA mutation have a 50% chance of carrying the same mutation. In a family with a known BRCA mutation, any person who is shown NOT to carry the mutation has the risk of developing cancer equal to that of the average person his/her age. It is also important to remember that both men AND women carry BRCA mutations, although medically there are different implications.

In the general population, BRCA1 and BRCA2 mutations are uncommon – about 1/800. They are found more frequently in families with strong histories of cancer, as described above. Specific mutations in the BRCA1 and BRCA2 genes are found more often among families of particular ethnic backgrounds. For example, approximately 1 in 40 Ashkenazi (Eastern European) Jewish individuals carries one of three specific BRCA1 and BRCA2 mutations. Among Ashkenazi Jewish women who have had breast cancer at a young age or ovarian cancer, the chance is even higher. More specifically, approximately 40% of Jewish women with ovarian cancer have a BRCA mutation, and 20% of Jewish women with pre-menopausal breast cancer, which is much higher than the non-Jewish population.

Determination of who should have genetic testing is based largely on the family history, or pedigree. Obtaining accurate medical records is imperative in this process. Additionally, statistical risk analysis tools are available to assist in clarifying an individual’s risk of carrying a BRCA mutation. For more information, please consider scheduling a consultation with a genetic counselor.

Following a discussion that consists of education about potential benefits, risks, and limitations of genetic testing, families may wish to proceed with BRCA mutation analysis. Each person needs to make his/her own decision about genetic testing. The testing also involves signing a consent solely for the purposes of genetic testing and providing a blood sample.

Cancernet - Genetic Testing
Genetichealth - Genetic Testing
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