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The majority of cancer is sporadic, however approximately 5 percent to 10 percent of all breast cancer and up to 10 percent of all ovarian cancer has an underlying hereditary or single gene cause such as a BRCA1 / 2 gene change. The chance that an individual has a BRCA1 / 2 gene change depends on:
Additionally, a significant proportion of breast cancers (15 percent to 20 percent) are familial in nature. This means that they are likely caused by a combination of genetic and environmental influences. In these cases, the risk for breast cancer may be increased within a family, but genetic testing may not accurately determine who is at risk, or the exact level of risk. Furthermore, some families may have a different, rarer genetic or hereditary risk factor other than a BRCA1 / 2 gene change. A genetic specialist can help to evaluate what type of testing may be appropriate for a specific family.
Women with a BRCA1 / 2 gene change have a 50 percent to 85 percent lifetime risk of breast cancer, and a 40 percent to 60 percent chance of a second primary breast cancer. There is also a lifetime risk of ovarian cancer of 10 percent to 45 percent. Men are at increased risk for male breast cancer and prostate cancer, and both men and women may be at increased risk for pancreatic cancer, melanoma and possibly other cancers.
Women who have a BRCA1 / 2 gene change should have annual mammograms and breast MRI starting at approximately age 25, as well as regular clinical breast exams. In addition, a medication known as Tamoxifen can help reduce the risk of breast cancer by about 50 percent in BRCA2 mutation carriers. Some studies have also shown reduction of risk in BRCA1 carriers; however the exact amount of risk reduction has not been confirmed. Lastly, prophylactic mastectomy (having both breasts removed before developing cancer) is an option that greatly reduces the risk of breast cancer. Less than 5 percent of BRCA carriers who have this surgery will go on to develop breast cancer of the remaining tissue.
Ovarian cancer screening currently includes transvaginal ultrasound and CA-125 blood testing every six to 12 months. This screening is neither sensitive nor specific, meaning that early stage ovarian cancer is often not detected through screening. Screening results can also be falsely positive when no cancer is present.
Women with BRCA1 / 2 gene changes who plan to have more children and / or are younger than age 35 should talk with their gynecologists about the benefits and limitations of this screening.
Otherwise, women with BRCA1 / 2 gene changes who do not plan to have more children and / or are older than age 35 are encouraged to consider prophylactic oophorectomy (having the ovaries and fallopian tubes removed before developing cancer). Fewer than 5 percent of women with BRCA genetic changes who have this surgery will go on to develop peritoneal cancer (a cancer similar to ovarian cancer). If performed before menopause, having the ovaries removed also reduces the risk of breast cancer by approximately 50 percent. In addition, there is evidence that oral contraceptive use for five or more years also reduces the risk of developing ovarian cancer.
If an individual has had cancer, there are three possible results from genetic testing:
If an individual has NOT had cancer, positive and uncertain results can be interpreted in the same way as the results in individuals who have had cancer (see the first and third possible results above).
However, there are two possible explanations for a negative result. First, there may be a BRCA1 / 2 mutation present in the family that explains the family history of cancer, but the person tested did not inherit the mutation. Alternatively, it may be that there is no BRCA1 / 2 mutation in the family. In this second case, everyone in the family may be at an increased risk of cancer, but there is no way to clarify the risk for individual members. Therefore all family members must be screened carefully based on the family history.
There is no way to distinguish between these two possible explanations without testing an affected family member. Therefore, if possible, it is recommended that a family member who has had a BRCA-associated cancer have testing first.
Both men and women can inherit BRCA1 / 2 gene changes and pass them on to their children. If an individual has a BRCA1 / 2 gene change, his or her child has a 50 percent chance of inheriting the same gene change. Likewise, siblings of an individual with a BRCA1 / 2 gene change also have a 50 percent chance of having the same gene change. If the individual’s children and / or siblings inherit the same gene change, they would then be at increased risk for the BRCA1 / 2 associated cancers. However, if an individual does not inherit a BRCA1 / 2 gene change that is known to be present in the family, that individual remains at the population risk for breast and other cancers and should follow population screening guidelines.
Alternatively, if individuals do NOT have a change in BRCA1 / 2, then their children cannot inherit such a genetic change from them. These genetic changes do not skip generations.
The Genetic Information Nondiscrimination Act (GINA) protects individuals enrolled in group or individual insurance plans from being denied coverage, dropped from a health insurance plan or denied employment based on genetic or family history information.
However, it does not apply to individuals who receive care through the Tricare military health system, the Indian Health Service or federal employee health benefits plans.
Genetic information cannot be considered to be a pre-existing condition. There are currently no laws protecting life or disability insurance.
In addition, GINA also makes it against the law for your employer to use family health history and genetic test results in making decisions about your employment. These protections apply to all employers with 15 or more employees, regardless if it is a not-for-profit organization or a corporation, but does not extend to the US military or employees of the federal government.
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