Most cancers happen by chance and there is no obvious inherited reason for them. However a small proportion of cancers occur as a result of a genetic predisposition because a gene passed down through generation of a family carries a mutation – this wasthe reason behind actress Angelina Jolie’s decision to opt for a double mastectomy last year.
People with a strong family history of cancer – especially if many members of their family have been diagnosed with cancer, especially at a young age – may be carrying one of these genes. That is why it is important for everyone to find out their family’s cancer history. It may be difficult to broach the subject with relatives, but talking about cancer among families has the power to prevent later problems, improve access to early treatment and raise awareness. Families with a high incidence of breast and ovarian cancers are one example.
In the 1990s, scientists discovered that germline mutations in the “BReast CAncer” genes (BRCA1 and BRCA2) caused familial breast and ovarian cancer. We now know thatmutations in BRCA1 or 2 account for around 10% of all ovarian cancers. Women who carry a BRCA1 gene mutation have up to a 90% lifetime risk of getting breast cancer, and up to 60% risk of ovarian cancer. For BRCA2 the rates are 80% and 30% respectively.
Members of BRCA-mutation carrying families may have developed their cancers at a younger age than the general population (for example when they were under 40). These are usually on one side of the family and can occasionally affect male relatives (causing male breast cancer) also. The mutation is passed down in a Mandelian fashion, which means a parent (either father or mother) who carries the mutation has a 50% chance of passing it to their children.
Fathers may be unaffected clinically but act as carriers and can pass the mutation to their children. The cancer therefore may skip a generation. If a person has breast or ovarian cancer they can have genetic testing in the form of a blood test to see if they carry BRCA gene defects. If a BRCA mutation is identified, other relatives that could potentially have inherited the mutation can be offered tests.
So how does it help to know whether carry a mutation? If you carry a BRCA mutation, you can significantly reduce your risk of getting breast or ovarian cancer by having surgery to remove these organs or have screening for breast cancer for early diagnosis. For example, removal of both ovaries dramatically reduces the risk of developing ovarian cancer. Similarly, a mastectomy is effective in reducing the risk of breast cancer. Deciding whether or not to have these operations is difficult, but knowing one’s genetic status is useful in making an informed choice.
Everyone has a different perception of risk, so some will opt for screening while others prefer surgery. The choices may be wide ranging. If a young woman finds out she has BRCA gene mutation, she may decide to have children at a younger age so that she can have her ovaries and breasts removed afterwards.
Although BRCA gene mutation is much talked about and has had a lot of publicity recently, there are other genetic predispositions that are worth mentioning. For example Lynch Syndrome may be inherited and passed on in families and can result in significant increase in risk of bowel cancer, endometrial cancer and ovarian cancer. There may be effective screening or chemo-preventative measures that can be offered such as colonoscopy for bowel cancer or mammography for breast cancer or use of aspirin in reducing risk of bowel cancer.
But knowing your family history is vitally important and as ovarian cancer awareness month draws to a close, what better time to think about talking to parents and grandparents about your family tree. If a person knows they have a mutation in any of these genes, they have the choice to make informed decisions about their health and future. Most people don’t leave important things to chance, why should we leave our health to chance? When it comes to cancer risk within families, it is definitely good to talk.