Is there a link between breast cancer and Jewish origin?
This page has information about the risk of inheriting a breast cancer gene fault if you have an Ashkenazi Jewish background. There is information about
- About the Ashkenazi Jewish population
- If you are worried but don't have an Ashkenazi background
- Faulty breast cancer genes in general
- Faulty breast cancer genes in the Ashkenazi Jewish population
- How much breast cancer genes increase your risk
- Having a family history of breast cancer
- About genetic testing for breast cancer
Ashkenazi Jewish people live all over the world now. But they originally came from northern and eastern Europe, mainly from regions in Germany, Russia and Poland. In the UK and America, most of the Jewish population are Ashkenazi.
Breast cancer is the most common cancer in women in the UK, so it isn’t unusual to have a relative who has had it. Sometimes breast cancer can run in families, but this is unusual. Most cases of breast cancer are sporadic, meaning they happen by chance. But a small percentage of women inherit a faulty breast cancer gene. This doesn't mean you will necessarily get cancer. But it will mean that you are more likely to than the average person.
We know of several genes associated with an inherited risk of developing breast cancer. The two most common breast cancer genes are BRCA 1 and BRCA 2. This stands for BReast CAncer gene number 1 or 2.
Everyone is born with BRCA1 and BRCA2 genes. Normally, these genes help protect cells from cancerous changes. But sometimes you can inherit an abnormal (mutated) form of BRCA1 or BRCA2 from your family. This doesn't mean you have cancer, or you definitely will get cancer. But it does mean that breast cancer is more likely because your breast cells are one step further along the road to becoming cancerous than they would be if you didn't have the gene fault.
Although only a few people inherit faulty BRCA genes, this is more likely to happen in people of Ashkenazi Jewish descent than in the general population. But even in this population, it still isn’t common.
We don’t know the exact numbers, but the best estimate is that about 1 in 40 Ashkenazi Jewish women (about 2.3%) carry a BRCA1 or BRCA2 gene fault. Again, we don’t know the exact incidence for the general population of women. But about 1 in 800 woman carry a BRCA1 mutation and 1 in 1,000 carry a BRCA2 gene fault. This means that overall, about 1 in 450 women in the general population have either BRCA1 or BRCA2 gene faults. So these faulty genes are likely to be about 10 times as common in Ashkenazi Jewish women.
There is no single fault that we can always look for. Several hundred different types of faults have been identified on BRCA 1 and BRCA 2. So it can be very difficult to find a breast cancer gene fault unless you have a relative with a known fault already. But in the Ashkenazi Jewish population, 3 specific gene faults tend to be seen more commonly (two in BRCA 1 and one in BRCA 2). This makes it easier to test for the faulty genes than other people with a strong family history because the testers know what to look for.
Your lifetime risk of getting breast cancer if you carry a BRCA1 and BRCA2 gene fault could be as much as 90%. That means as many as 90 out of every 100 women with one of these faults will get breast cancer at some point in their lives. As with breast cancer risk generally, the risk increases with age. Half of all women who carry a faulty breast cancer gene will have developed breast cancer by the time they are 50 years old.
We can’t say your lifetime risk is definitely 90% because the actual risk can vary between families. Having one of these faulty genes means you are more likely to get breast cancer than someone who does not carry the gene fault. But it is not a certainty. Genes for any characteristic do not always show up in an individual. This is called gene expression or penetrance. This can be affected by other genes that you carry, or by any other breast cancer risk factor, such as lifestyle or environmental exposure to anything else that may cause cancer.
Some research indicates that the breast cancer incidence in Ashkenazi women with these gene mutations is lower than for other women with these mutations. The lifetime risk of breast cancer may be only about 60 out of 100 women with BRCA1 mutations. And it may be as low as 40 out of 100 for BRCA2 mutations.
Remember that most breast cancers happen by chance. Only about 5 out of every hundred are related to a known inherited breast cancer gene. The older you or your relatives are when diagnosed, the less likely it is that an inherited gene is the direct cause. On the page about breast cancer genes there is more information about understanding lifetime risk, getting tested and your options if you carry a gene. This is in the risks and causes of breast cancer section.
Women carrying a BRCA 1 or 2 gene fault also have a higher than usual risk of developing ovarian cancer. We don’t know the exact risk, but somewhere between 10 and 60 out of every 100 women with these gene faults get ovarian cancer (10 to 60%). For an average group of women without BRCA gene faults, about 2 in 100 will get ovarian cancer (2%).
Some women with a family history of breast cancer will not be at any greater risk than the rest of the population but others may have more of a risk. If you are thought to be at a higher than average risk, you may be offered breast screening with mammograms at an earlier age than usual (from 40 rather than 50). If you have a family history of breast cancer and ovarian cancer and are of Ashkenazi descent then you may also be able to have genetic tests for the BRCA 1 and 2 genes.
If you have a family history of breast cancer or ovarian cancer, or both, then you should talk to your GP. They can check your family history with you and decide whether or not you need to be referred to a specialist breast care team for further assessment. The National Institute for Clinical Excellence (NICE) published guidelines in July 2006 on looking after women with a family history of breast cancer. You can see the NICE guidelines on familial breast cancer on this link or ask them to send you a copy in the post. These guidelines recommend that GP’s always seek advice from specialist breast cancer services for women of Jewish descent who have breast cancer in the family.
Generally, it is only possible to have a test for BRCA 1 and BRCA 2 if you have a strong family history of breast cancer and preferably a living relative with breast cancer. But it is different for Ashkenazi Jewish women. They tend to have one of 3 very particular gene mutations and people testing the genes know exactly where they are. This makes the gene faults much easier to find. So you don’t need to have a living relative with breast cancer.
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