The communication of information on cancer risk and carrier probability is not straightforward. There is a degree of uncertainty with respect to the probability of inheriting a predisposing genetic mutation, of gene penetrance and hence of developing cancer. People who are concerned about a family history of breast cancer may require information to help them deal with the complex medical and social choices linked with different levels of breast cancer risk management options, and support to cope with the associated uncertainty and anxiety. It is therefore not appropriate to develop a general population based screening programme for the presence of genetic mutations.
Breast cancer is the most common invasive cancer diagnosed in women in Ireland. A comprehensive symptomatic breast service is available for women in the eight designated cancer centres. Most cases of breast cancer arise in women with no apparent close family history. The majority of people with a family history of breast cancer will not be at substantially increased risk.
However, five to ten per cent of all breast cancers are explained by the presence of BRCA1 or BRCA2 mutations. The lifetime risk of breast cancer in these women may be as high as 80%. However, not all familial clusters can be explained by known breast cancer susceptibility genes such as BRCA1 or BRCA2.
The National Cancer Control Programme (NCCP) established a National Hereditary Cancer Programme in 2011 with the National Centre for Medical Genetics in Crumlin Hospital. Additional genetic testing clinics have been established in St James's and the Mater Hospitals in Dublin - with a similar service due to be opened in Cork University Hospital in the coming months. In 2012 the new clinics in the Mater and St James's Hospitals assessed and tested almost 200 women (with breast or ovarian cancer) for the BRCA gene mutation. This represents more than a 100% increase in the numbers of women tested nationally compared with 2011.
There are two groups of women involved – those who have been diagnosed with cancer and those who have a family member who has been found to carry a gene mutation. Testing is undertaken on the basis of agreed medical criteria and is always preceded by genetic counselling. The NCCP and National Centre for Medical Genetics are continuing to work to ensure that the service is expanded to meet national needs.
Accurate predictive breast cancer genetic testing on a healthy woman with a family history of breast cancer is not clinically useful, unless a specific gene alteration has been identified in an affected family member. Well women without a personal history of breast cancer who are concerned about their family history should in the first instance discuss their concerns with their family doctor. The GP will want to know details of the family history and any information available in relation to genetic testing of relatives. The GP may then refer the patient to a specialist secondary care service such as a Symptomatic Breast Disease Unit, if there are features highly suggestive of familial disease, for more detailed assessment.