Breast cancer in the family: what are the chances?
Around one in eight Australian women will develop breast cancer by the time they are 80. When a diagnosis of breast cancer occurs, many family members worry that there may be an inherited genetic link. So how do you know whether your family is at risk?
According to Epworth Specialist Breast and Oncoplastic Surgeon, Miss Jane O’Brien, the most powerful predictors of having a genetic link to breast cancer in the family are multiple cases of breast cancer on the same side of the family, and young age at the time of breast cancer diagnosis.
There are two genes associated with familial breast cancer, BRCA1 and BRCA2. Only 5–10% of all breast cancers are related to an inherited genetic abnormality, and less than 1% of the population have a mutation in one of the major breast cancer predisposition genes, BRCA1 and BRCA2.
“While the average lifetime risk of breast cancer until age 85 for Australian women is around 10–12%, for the very small proportion of the population who do have a BRCA mutation, the lifetime risk may be up to 80% or more, as well as a 40–50% lifetime risk of ovarian cancer,” Jane says.
“In our risk assessment we look for the presence of features suggestive of a BRCA mutation within a family, which are multiple cases of breast cancer on the same side of the family. We also look for early onset (before turning forty), ovarian cancer in a family, both breast and ovarian cancer in the same woman, cancer in both breasts, Ashkenazi Jewish heritage, and male breast cancer.”
For families where breast cancer is present, doctors perform a risk assessment to determine whether the family history gives them a mildly elevated risk, a moderate risk or high increased risk of developing breast cancer.
Even when the mutation of the BRCA gene is present in a family, there is still only a 50% likelihood that individual family members will inherit that mutation. You therefore may have families where some members of the same generation have the gene and others don’t.
Jane says the importance of doing a thorough risk assessment lies in the fact that testing for a genetic mutation in the general population is like looking for a spelling error in a set of encyclopaedia.
The process for determining whether you have any case for genetic testing involves starting with your General Practitioner (GP). They may refer you to a specialist to do a more thorough risk assessment.
You may then be referred to the genetics team at a familial cancer centre, who will then make a decision as to whether to offer genetic testing.
Jane says that for most women, there is only, at most, a mildly elevated risk, and that the regular breast screening programs in place in Australia are the appropriate level of screening.
“All women can also reduce their risk of developing breast cancer through exercise, weight control and minimising alcohol consumption,” she says.
Those with a moderately increased risk may undertake regular screening, but perhaps more frequently.
Those with a proven BRCA mutation may need to consider risk reduction strategies such as medication or even risk-reducing surgery such as bilateral mastectomy, and removal of the fallopian tubes and ovaries.
There are many Family Cancer Clinics around Australia that provide support to families dealing with cancer. Go to canceraustralia.gov.au for more information.
The Epworth Women’s Health Clinic provides GP services with breast screening and specialist referral on site.
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