Breast Cancer and Genetics
1 in 8 women (12 %) will be diagnosed with breast cancer in their lifetime. However about 5-10% of breast cancers are hereditary or passed down through families by abnormal genes. Genes are found in all cells in our DNA and act to instruct each cell to grow and perform tasks based on their location and required function in the body. When one of the genes becomes abnormal then a cell may not grow or function properly. In some patients who are diagnosed with breast cancer, the cells in their breast tissue may have an abnormal gene causing the cells to become cancerous. The following may alert your physician that you may have an abnormal gene causing your breast cancer:
- Multiple blood relatives (grandmothers, mother, sisters, aunts) on either your maternal or paternal side of the family who was diagnosed with breast or ovarian cancer before age 50
- You have relatives with both breast and ovarian cancer on the same side of the family or in a single individual, or a male with breast cancer, or a female with bilateral breast cancer
- You are of Ashkenazi Jewish (Eastern European) heritage.
- You have a relative(s) with triple receptor-negative breast cancer.
- There are other cancers in your family in addition to breasts, such as prostate, melanoma, pancreatic, stomach, uterine, thyroid, colon, and/or sarcoma.
- You are African American and have been diagnosed with breast cancer at age 35 or younger.
What genetic abnormalities are associated with an increased risk of breast cancer?
The most common inherited abnormal genes associated with breast cancer are the BRCA1 and BRCA2 genes. Everyone has these genes which work to repair damage within cells. But when these genes become abnormal, they do not function properly and cannot repair damage resulting in potential cancer transformation in the breast, ovarian, and other tissues. Not everyone who inherits these abnormal genes will develop cancer, but they do have up to an 80 % risk of developing breast cancer in their lifetime (BRCA1- 50-70%, BRCA2 40-60%). Often these patients will develop breast cancer at a younger age, in both breasts, and may need more aggressive surgical treatments. Women with the BRCA1 or BRCA2 gene may also be at higher risk for other cancers such as ovarian, colon, melanoma, and pancreatic cancers. Men with the BRCA1 and BRCA2 genes are at higher risk for breast, prostate, skin, and digestive cancers. Remember men can get breast cancer too!
Other common abnormal genes associated with cancer risk include:
- TP53 – makes protein to stop tumor growth- Li-Fraumeni syndrome- increases risk breast cancer, leukemia, brain tumors, sarcoma- cancer risk with Li-Fraumeni is 100% in women and 73% in men.
- ATM – repairs DNA and when abnormal increases risk for breast and pancreatic cancer- associated with ataxia-telangiectasia disease
- PALB2 – repairs DNA and stops tumor growth and works closely with the BRCA2 gene- women have 33-58% increased lifetime risk of developing breast cancer
- PTEN – helps regulate cell growth- associated with Cowden’s disease (also SEC23B gene) – higher risk of both benign and cancer of the breast (85%)- also associated with growths of the digestive tract, thyroid, uterus and ovaries
- RAD50, MRE11A, NBN – all genes that form the MRN complex that helps repair damage to DNA – all increase risk of breast cancer (NBN highest association)
- CDH1 – makes a protein that binds tissue together- increase the risk of stomach cancer (83%) – increased lifetime risk of invasive lobular breast cancer in women (39-52%)
- CHEK2 – makes protein to stop tumor growth- increased risk of prostate cancer and doubles the risk of colon and breast cancer
- STK11 – regulates the growth of cells- causes Peutz Jegher syndrome to increase risk gastrointestinal, ovarian, breast, and lung cancers.
- BRIP1 – repairs DNA – increases risk of ovarian and breast cancers
If I have inherited an abnormal gene, what does this mean?
For those patients already diagnosed with breast cancer, treatment will progress based on the gene inherited, type of breast cancer, stage of the disease, and age of the patient. You may also receive a recommendation to remove the breast that does not have cancer (known as a prophylactic mastectomy) because of your increased risk for breast cancer. Other screening and possible surgical recommendations may be made by your physician based on the specific abnormal gene inherited. For those patients without a diagnosis of breast cancer but with an abnormal gene, your physician may discuss placing you on a screening program to monitor you closely with more frequent exams (i.e. mammograms, MRI’s and Ultrasounds), placing you on hormonal therapies or may discuss prophylactic surgeries to remove the tissues that carry the abnormal genes to prevent the development of cancer.
For many patients diagnosed with an abnormal gene, feelings of fear, guilt, anger, and concern for the future of your family and your health may exist. These are very normal feelings and therefore it is important to seek support and counseling through your physicians and the community.
How does my physician find out if I have hereditary breast cancer?
Your physician will do a thorough family history so knowing any blood relatives especially the first degree that has been diagnosed with cancer is important. In addition, your physician may refer you to a genetic counselor who specializes in looking at your family tree and medical history to help determine if you have inherited an abnormal gene. If the suspicion is high, then a blood test will be ordered which will look at your DNA and screen if you have any abnormal genes. This test often takes 2 – 6 weeks to come back. The test only screens for a limited number of abnormal genes, so if the result returns negative but you have an extensive family history of cancer, you may still have hereditary breast cancer from an abnormal gene yet to be discovered.
Questions to Ask
- Could my cancer be inherited and if so, what does this mean for me, my family, and my treatment?
- What other cancers am I at risk for and how will I be screened?
- Do I need genetic testing done and will my insurance cover the cost of the test?
- How do I counsel my children and family once I have the results?