[Risk assessment for familial occurrence of breast cancer].

There is now unequivocal evidence that an estimated 5% of breast cancer cases is inherited in families. Inherited predisposition of cancer in these families is thought to be the result of a mutation in one of several highly penetrant autosomal dominant genes such as BRCA1 or BRCA2. The BRCA1 gene which is localized on chromosome 17 q was recently isolated and at about the same time BRCA2 was localized to chromosome 13 q. A number of other genetic mutations is also associated with predisposition to breast cancer but accounts for a very small proportion of inherited breast cancer. Many women want to know whether they have inherited a gene predisposing to breast cancer. Those with a family history of breast cancer are particularly concerned about their risk of disease. Currently the assessment of an individual's risk of breast cancer can be undertaken using prediction models based on family history and can be further refined when molecular genetic investigations became available. Without molecular characterisation the Claus tables derived from the Cancer and Steroid Hormone Study data set are best suited to predict breast cancer risk based on age of onset of affected relatives. Direct screening for mutations in breast cancer genes in not yet generally available. Testing for inherited susceptibility is currently being offered to selected families where multiple cases of breast and/or ovarian cancer are diagnosed at an early age (younger than 45 years) as part of research protocols. In these families the so-called indirect gene analysis for linkage of disease to BRCA1 and BRCA2 or the direct analysis of mutations with functional significance in the BRCA1 gene allows relatively refined risk assessment for non-diseased female family members. Some examples will be presented to illustrate risk assessment in different familial and individual situations. Risk assessment including test result interpretation and counselling can be appropriately provided directly to the patient by physicians and genetic counsellors in a coordinated genetic counselling setting.