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Cancer Genetics

Risks of Breast Cancer

01/22/1999

Question:

I had breast cancer at the age of 45. What does this mean for my daughter (now 23)? Should she get tested for the breast cancer gene? What if she has it? Would that mean she shouldn't have children? What about my son? He already has a daughter (now 1.5 y.o.). Should my son be tested, or should his daughter be tested? Can a son pass along the breast cancer gene to his daughters? Can a son be at risk for breast cancer too?

Answer:

The fact that you had breast cancer at the age of 45 will increase your daughter's risk for developing breast cancer somewhat. However, in order to determine your daughter's precise breast cancer risk we would need to know more about your family history of cancer and your daughter's personal medical history. I would recommend that if you are of Ashkenazi Jewish descent (your ancestors are from Eastern Europe and are Jewish) OR if you have any other relatives with breast or ovarian cancer, you and your daughter should consult with a genetic counselor who can evaluate the family history, determine the likelihood that you have hereditary breast cancer, give your daughter an accurate estimate of her lifetime risk for the development of breast cancer, and discuss the pros and cons of genetic testing. The National Cancer Institute's Genetic Counselor Service is listed below as an additional Web site. It can help you locate a genetic counselor in your region. If you do not have any other family history of breast or ovarian cancer and your family is not of Ashkenazi Jewish descent, the likelihood that you have hereditary breast cancer is extremely low. In this case, we can estimate your daughter's lifetime risk for the development of breast cancer based on large studies of women with a similar family history. These studies found that a woman with a mother diagnosed with breast cancer in her 40s has a 13.2% lifetime risk for breast cancer compared to 10% in the general population. (Note - This risk figure will be an underestimate if your daughter has any additional risk factors for breast cancer, for example a prior breast biopsy with atypical hyperplasia.) The decision whether or not to undergo genetic testing for the breast cancer genes is a difficult one. There are many considerations including: the likelihood that the family has a change in one of the breast cancer predisposition genes, whether or not the genetic test result would change an individual's medical management, the expense of the test, and the risk for insurance discrimination. In general, we begin genetic testing in any family by testing one of the relatives who has had cancer. Therefore, if testing is indicated in your family based on your family history, we would recommend that you begin the genetic testing process rather than your daughter. If you were found to have a genetic alteration that caused your breast cancer, then accurate genetic testing could be provided to your daughter. If you were found to have a genetic alteration that caused your breast cancer, your daughter and your son would each have a 50% chance of inheriting the responsible gene. If they did not inherit the responsible gene, they would have no increased risk for cancer and they could not pass it on to their children. If they did inherit the responsible gene, then they would have an increased risk for the associated cancers (listed below) and they would have a 50% chance of passing the gene on to their children. So, in fact, if you have a breast cancer predisposition gene and your son inherited it - he could have passed that gene on to his daughter. However, there is ABSOLUTELY no reason that your daughter or son should not have children if they are found to have a breast cancer predisposition gene. The diagnosis and treatment of cancer are progressing at an amazing rate. Who knows what will be available to your grandchildren by the time they are old enough to be concerned about their risk for cancer? Here is some information about the breast cancer genes and their associated cancer risks: BREAST CANCER GENES: The breast cancer susceptibility gene, BRCA1, is located on chromosome 17q. Alterations in this gene account for up to 25% of hereditary breast cancer cases. Individuals with such alterations are at increased risk for breast, ovarian, and prostate cancers. It is reported that women who carry alterations in the BRCA1 gene have up to an 85% lifetime risk to develop breast cancer and a 40-60% lifetime risk to develop ovarian cancer. This is compared to the 10% lifetime risk of breast cancer and 1-2% lifetime risk of ovarian cancer observed in the general population. BRCA1 carriers, who have had breast cancer treated with mastectomy, have up to a 64% risk of contralateral breast cancer (cancer in their other breast) by age 70. Both men and women who carry alterations in BRCA1 have a 6% risk to develop colon cancer by age 70. Males who carry alterations in BRCA1 do not appear to be at increased risk for breast cancer, but are at increased risk for prostate cancer. This risk is estimated to be 8% by age 70. The BRCA2 gene is located on chromosome 13q. Mutations in this gene account for up to 15% of families with hereditary breast cancer. Women who carry alterations in BRCA2 have up to an 85% lifetime risk to develop breast cancer and are at increased risk for ovarian cancer. The ovarian cancer risk is less well known, but is estimated to be between 15 and 20%. Males who carry alterations in BRCA2 are estimated to have a 5-10% risk of breast cancer. A wider tumor spectrum including cancers of the pancreas, prostate, and colon may be associated with BRCA2 alterations. Further research is ongoing to better define the disease spectrum and the attendant risks.

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Response by:

Heather L Hampel, MS, CGC Heather L Hampel, MS, CGC
Cancer Genetic Counselor
College of Medicine
The Ohio State University

Judith A Westman, MD Judith A Westman, MD
Associate Professor, Clinical Internal Medicine, Pediatrics and Medical Biochemistry
College of Medicine
The Ohio State University