Inherited mutations in BRCA1 and BRCA2 genes increase the risk of female breast and ovarian cancers, and to a lesser degree, other cancers in men and women.
What is the BRCA gene?
BRCA stands for BReast CAncer. We all carry the two BRCA genes, BRCA1 and BRCA2. These genes produce tumour suppressor proteins that repair other genes. If this process isn’t working properly, damaged genes don’t get repaired, which can lead to cancer.
Some of these gene mutations happen to one person. Others, such as BRCA mutations, are passed on from one generation to the next. That’s why you’re more likely to carry a BRCA mutation if other close family members have had certain cancers.
Why are BRCA gene mutations important?
The BRCA gene is one way the body stops cancer from developing. If a woman has one of the important BRCA mutations, she is about five times more likely than the rest of the community to develop breast cancer and between 10 to 30 times more likely to develop ovarian cancer. People with a BRCA gene mutation also have an increased risk of colon cancer, pancreatic cancer and prostate cancer.
How do I know if I carry a BRCA gene?
You are more likely to carry an important mutation in the BRCA gene:
- the more family members with breast or ovarian cancer you have
- the younger you are when you get cancer.
There are three reasons to be tested for a BRCA mutation:
- if you develop one of the types of cancers mentioned above, especially ovarian or breast cancer and other family members have had cancers
- if you have not had cancer but several close family members have
- if a close family member is tested and found to have a BRCA mutation.
Note: Family members in this case means blood relatives only.
For more information about whether you should get a BRCA gene test (Breast Cancer Foundation NZ). In New Zealand, you will be counselled about the implications of being tested beforehand.
I have been tested and found to have a BRCA gene. Now what?
Not all BRCA mutations are the same. Some, called deleterious mutations, increase your risk of developing breast or ovarian cancer a lot. Others don’t increase your risk much above the general population risk.
If you were tested because you have cancer, your treatment will probably be similar to patients without the BRCA mutation, as it is just one factor that doctors use to decide on the best course of treatment for you.
Screening for breast cancer
Women with deleterious BRCA mutations are offered screening for breast and ovarian cancer.
Mammograms are usually used to screen for breast cancer, but in young women with BRCA mutations, an MRI scan is usually performed, as this is considered safer than yearly mammograms. Ultrasound scans are occasionally used, and studies are underway to identify breast cancer using a blood test.
Ovarian cancer is screened for using ultrasound scans of a woman’s pelvis. This is usually combined with a blood test called Ca-125.
The aim of screening is to find a cancer when it is small because survival depends mostly on how much a cancer has grown or spread before it is removed. Women who have breast or ovarian cancers removed early have an excellent chance of long-term survival.
Some women decide that the risk of developing a cancer is so high, that they have an operation to remove their ovaries and breasts. This is called prophylactic (preventative) surgery. This is a huge decision, but evidence from medical trials suggests that it can prevent a woman with a deleterious BRCA mutation from developing breast or ovarian cancer.
What can you do to prevent breast or ovarian cancer?
Even if you have a BRCA mutation, you can decrease your chance of developing breast cancer by:
- having your babies younger and breastfeeding them
- staying a healthy weight (a BMI between 20–25)
- getting regular exercise
- not smoking or drinking too much alcohol.
You can decrease your chance of developing ovarian cancer by:
- using the combined contraceptive pill
- having children.
The effect of hormone replacement therapy (HRT) on breast and ovarian cancer risk is uncertain.
Breast cancer NZ Breast Cancer Foundation
Genetic testing – why was I referred? NZ Genetic Health Service
Familial breast cancer – classification, care and managing breast cancer and related risks in people with a family history of breast cancer National Institute for Health and Care Excellence guidelines, NZ
Breast cancer Breastcancer.org, US
|Dr Jeremy Tuohy is an Obstetrician and Gynaecologist with a special interest in Maternal and Fetal Medicine. Jeremy has been a lecturer at the University of Otago, Clinical leader of Ultrasound and Maternal and Fetal Medicine at Capital and Coast DHB, and has practiced as a private obstetrician. He is currently completing his PhD in Obstetric Medicine at the Liggins Institute, University of Auckland.|