Some public health issues in the current state of genetic testing for breast cancer in Australia.

Two genes associated with a high breast cancer risk (BRCA1 and BRCA2) have been discovered recently from study of large breast-cancer-dense kindreds. It is problematic to make inferences from these atypical families to the general population. Nevertheless, it appears that about 1 to 2 per cent of all breast cancer may be due to rare deleterious mutations in BRCA1 or BRCA2. The majority of breast cancer families with fewer than four cases are likely to have cancers not attributable to these genes. There may be more common mutations in other genes (such as ATM, HRAS1) that confer a moderate risk of breast cancer, and may account for 5 to 15 per cent of cases. At this early stage of cancer genetics, the risks associated with particular mutations are not known, there are no proven and acceptable strategies for women with an inherited susceptibility to ameliorate risk or improve prognosis, and risk estimates appropriate for Australian women with a family history of breast cancer are not established, although data from the United States may overestimate risk. Information is needed from population-based studies, such as the Australian Breast Cancer Family Study (Hopper et al. Breast 1994; 3: 79-86), but 100 per cent mutation detection in large cancer genes is difficult and expensive. Development of a systematic, research-oriented, evidence-based approach to genetic testing in Australia is recommended. Australia could lead the world in having common protocols used in breast cancer clinics across the country, linked to a national research consortium and database.