Questions about inherited breast cancer and BRCA1 and BRCA2? Here are some pointers
Recent media coverage about Angelina Jolie and her decision to opt for bilateral mastectomy has highlighted the issue of genetic breast cancer and the genes BRCA1 and BRCA2. Here is some useful information which may help you better understand some more about it and perhaps answer some of your questions.
Is genetic breast cancer common?
No. it is rare. Breast cancer is the commonest cancer in women (apart from skin cancer) and affects about 3,000 women in Ireland each year. Only about 5% of those cancers are genetic.
What is genetic breast cancer and how do faulty genes increase my risk?
Genetic breast cancer is a type of breast cancer which can occur when a faulty gene is passed on from either parent. A cell needs to have a number of mistakes in its genetic code before it becomes cancerous. These mistakes or faults are called mutations. Mutations can occur during a person’s life due to substances we come into contact with that cause cancer, for example, Cigarette smoke. They can also happen because of mistakes that cells make when copying their genetic code before dividing into two new cells. Most of these abnormal cells die or are killed off by your immune system. It usually takes many years to gather enough genetic mistakes, so this is one of the reasons that cancer is generally more common as we get older. It is possible to be born with a gene fault that may increase the risk of cancer. This doesn't mean you will definitely get cancer. But it means that you are more likely to develop cancer than the average person.
What are BRCA1 and BRCA2 and what do they mean?
In the mid- nineties, two high-risk predisposing genes, BRCA1 and BRCA2 were identified by researchers looking at younger women with strong family histories. BRCA1 and BRCA2 mutations are inherited in a particular manner, which means that if a person has a mutation present in the gene, their offspring have a 50% chance of inheriting it. Women who have a mutation in either of these genes have a 50–85% lifetime risk of developing breast cancer and a 10–40% lifetime risk of developing ovarian cancer. If either one of these mutations are found it carries an increased risk of a second breast cancer.
What kind of family history might be relevant?
Here is a list of the types of family histories that may be of concern and if you identify with any of these as detailed, it would be best to discuss with your GP. He can refer you on a clinic where you have your risk assessed and make arrangements for testing if appropriate.
1st degree relatives are: mother, father, brothers or sisters.
2nd degree relatives are: aunts, uncles, nieces, nephews, grandparents and grandchildren.
Breast cancer
- Two 1st degree relatives diagnosed before average age 50 years
- One 1st degree relative plus one 2nd degree relative diagnosed before an average age of 50yrs
- Three 1st or 2nd degree relatives diagnosed before the average age 60
- Four relatives diagnosed at any age
- In some cases one relative who developed breast cancer younger than 40 years
- Women with Ashkenazi Jewish ancestry
Ovarian Cancer
One relative diagnosed with ovarian cancer at any age and where on the same side of the family there is also:
- One 1st degree or 2nd degree relative with a breast cancer diagnosed before 50 years
- Two 1st degree or 2nd degree relatives diagnosed with breast cancer younger than average age of 60 yrs
- Another relative on the same side of the family with an ovarian cancer at any age of diagnosis
Bilateral Breast cancer
One 1st degree relative with cancer diagnosed in both breasts at a younger than average age of 50 years and where on the same side of the family there is also:
- One 1st or 2nd degree relative diagnosed with breast cancer before the average age of 60 years.
Male Breast Cancer
A man diagnosed with breast cancer at any age and where on the same side of the family there is also:
- One 1st or 2nd degree relative diagnosed with breast cancer before the age of 50 years
- Two 1st or 2nd degree relatives diagnosed with breast cancer before average age of 60 years
What does genetic testing involve?
It is a blood test and usually offered to those with a diagnosis of cancer with a strong family history. If a genetic mutation is found the test is offered to the person’s relatives. This is because looking for a gene fault is like looking for a single spelling mistake in a very long book. The initial test is looking for which fault on the breast cancer genes might run in your family. If a faulty gene is found, the test can then look for that same gene fault in you. With particular groups of women, there are very common specific gene faults. Ashkenazi Jewish women commonly have one of three particular genetic mutations.
Considering a genetic test
Before you decide whether or not to go ahead with the test, the nurse counsellor at the clinic will make sure that you have good information to take away, read, and think about. Having a test can have a big impact on you and other members of your family. The nurse will try to answer all the questions you have about the test. There’s no rush and you can take as long as you need to make up your mind whether to go ahead or not. The important thing is that you feel you have been given enough information to make the right choice about whether to have the test. Talk it over with a good friend or relative. Or if you feel you need to talk with your Doctor, you can get back in touch with them. Even if you know it is possible, finding out that you have a high risk of breast cancer may still come as a shock. You need to be sure that you want to know the test result before you go ahead. And you also need to be sure that you will be able to decide everyone is different and there is no right or wrong way to feel about this.
