Breast cancer genetics - Implications for clinical practice

The genetic basis for all breast cancers is beginning to be unraveled. Brea st cancer results from gene mutations which are either present in the germl ine of the affected individual or which are acquired in the breast cells. T he true proportion of breast cancers caused by germline mutations in genes causing predisposition to breast cancer remains to be determined. Twenty pe rcent to 30% of all women with breast cancer have at least one relative wit h the disease, but it is currently estimated that only 5% to 10% of cases a re caused by inheritance of germline mutations in highly penetrant suscepti bility genes such as BRCA1 and BRCA2.(18-20, 92) Individuals who inherit BR CA1 and BRCA2 mutations can now have a more accurate risk assessment with g enetic testing. Testing for amplification of the HEX-2/neu gene in breast t issues also has predictive value and can influence the choice of treatment. Thus, it is likely that an understanding of genetics will become increasin gly relevant in the management of persons who develop breast cancer, especi ally as strategies for both primary and secondary prevention are developed.