Inherited Breast Cancer
Plays Very Small Role in Breast Cancer In the last 10 years, cancer predisposing genes have been identified and cloned and it is now possible to offer predictive DNA testing to women with breast cacner and family
members at high risk for this disease.With the cloning of BRCA 1 and 2 genes that predispose to breast and ovarian cancer, a small storm has blown up. The risks have not been clearly defined and there is no known
100% effective intervention to offer those with a positive result. The information is controversial and has challenged both the public and the doctors. The facts are: 1- Only 5-10 % of breast and ovarian cancer is
inherited, meaning the majority of women who develop breast and/or ovarian cancer do not have the genetic mutation. Patterns that suggest that breast cancer may have been inherited include women diagnosed with
breast cancer at a young age (< age 45). 2- We all have the BRCA 1 and 2 genes, which are located on chromosome 13 and 17, respectively. A mutation in the form of
extra DNA or loss of DNA that occurs in the gene is a problem. 3- If you have the genetic mutation, the risks for breast and ovarian cancer are much higher: For instance, a 30 year old woman has
about a 1 in 2,525 chance of developing breast cancer and with the mutation, the risk can be as high as 1 in 3. Over a lifetime the risk ranges between 50 - 85% and you are not guaranteed to get it even
if you have the mutation. Everyone is born with 2 copies of each gene.Each gene contains a list of instructions. In the case of the BRCA genes- they are called suppressor genes, and contain instructions that suppress
uncontrolled breast cell growth. It takes 2 injuries to totally disable a gene - - which in this case could allow uncontrolled growth of breast cell, hence cancer. Hereditary
breast cancer means that you are born with one injured gene and it takes fewer steps to develop breast cancer than in non-hereditary breast cancer where one acquires two injured or damaged genes.
4- It is important to know your family history of cancer. You can inherit the genetic mutation from your mother or father. If either one of your parent carry the gene, there is a 50% chance of inheriting
the mutation regardless of the child's sex. This doesn't mean the child will develop cancer, it means that they will have inherited one of the injured genes. 5- There are populations at higher risk of finding the genetic mutation. For instance, Ashkenazi Jews (from Central and Eastern
Europe), which comprise almost 90% of Jews in the United States, people from Norway and Iceland have been found to have a higher incidence of carrying the mutation.
About 1 in 40 Ashkenazi Jews carries the genetic mutation (BRCA 1 or 2). 6- Genetic testing (finding out if one carries the cancer predisposing gene)is not a routine blood test and there are things
that genetic testing tells us and doesn't tell us. Here are the limitations: a- the particular mutation may not be tested- remember that there could be thousands out there, however only a few have been found.
b- a negative result is conclusive only when the correct mutation has been tested ( what if the mutation in that particular family was not tested ?)
c- the risk if you are carrying the mutation is not clearly defined- with reports ranging from 50-85 % of developing breast cancer. d- if you do have the mutation, there is no effective intervention that
assures you 100% freedom from developing breast cancer (see options below) e- negative results do not guarantee freedom from breast cancer mutated (your risk is the same as the general population without the gene).
f- positive results may provide incomplete information 7- Who should be tested ? In 1996, the American Society of Clinical Oncology recommended that gene testing for breast cancer be offered only to patients with a
"strong family history of cancer or very early age of onset of disease" In general, these are women who: a- were diagnosed with breast cancer before age 45 and have a
relative who had ovarian cancer at any age, or breast cancer at age less than 50 b- were diagnosed with both breast and ovarian cancer, ovarian cancer at any age, or with breast cancer before the age of 50
regardless of family history c- have a relative who has previously been tested and found to have a BRCA1/2 mutation d- come from a family in which breast and/or ovarian cancer has
affected multiple relatives in the same bloodline across several generations e- have 2 or more relatives on either the mother's or father's side of the family who has breast cancer at age less than 50 or ovarian
cancer at any age f- have a relative with male cancer at any age Remember that if you do not have breast or ovarian cancer and have a family history (as above), it would be recommended that the
person in the family with the cancer, if they are alive, be tested first. The genetic test usually entails 3 one hour sessions with a genetic counselor. For information on the National Society of Genetic
Counselors, please click on www.nsgc.org
, The first visit: to discuss what the test is about, your risk (they will make a pedigree chart or "family tree"), the implications for the test (medical, psychological,
social, employability and insurance issues of a discriminatory nature), what positive results mean and what negative results mean. The second visit: to perform the blood test if you decide to go
through with it, and the third visit: to discuss the actual results. This should be kept confidential and usually you are given a number to keep it anonymous.8- If you test positive for the genetic mutation:
a- you have a higher risk of developing breast and/or ovarian cancer b- your relatives may have a higher risk of carrying the mutation c- medical intervention should be considered and these include:
>close surveillance with diagnostic tests and clinical exams >lifestyle changes (eating healthier, exercising more, and watching your weight)
>taking a drug that reduces the risk for breast cancer such as tamoxifen, an antiestrogen, or joining a trial looking at tamoxifen or raloxifene (the STAR trial) if you are post-menopausal. Raloxifene is a "selective estrogen receptor modulator" that is effective in osteoporosis and is
being looked at as an agent to reduce breast cancer in high risk women. >taking a drug that may reduce the risk of ovarian cancer (such as birth control pills)
>preventive surgery such a removal of both breasts or ovaries
d- relief from uncertainty e- opportunity to be proactive (see c) f- enabling other family members to decide if they want testing g- psychological, employment and insurance issues
9- If you test negative for the genetic mutation assuming the correct mutation was tested: a- reduction from high risk to average risk (as in the general population) b- relief from anxiety
c- increased cancer screening unnecessary d- possible "survivor guilt" e- false reassurance that the risk for cancer is eliminated, you still need mamograms at age 40 and over, and breast exams!!
10- If you would like more information please call the NCI at 1-800-4-CANCER and request a copy of the booklet "Understanding Gene Testing" (NIH Publication No.97-3905) or http://www.nci.nih.gov or http:www.myriad.com or
cancernet.nci.nih.gov/wwwprot/genetic/generch.shtml. |
