Genetic risk of breast cancer.

Several cutting-edge strategies are being used to evaluate candidate genetic risk factors for breast cancer. These include linkage analysis for mapping out BRCA1 and BRCA2, mutational screening of candidate risk genes like CHEK2, ATM, BRIP1 and PALB2, which are associated with an intermediate level of breast cancer risk. Genome-wide association studies have revealed several low-penetrance breast cancer risk alleles. The predisposition factors are associated with different levels of breast cancer risk. Relative to control population, the risk in patients harboring high-risk BRCA1 and 2 mutations is over 10-fold, with intermediate penetrance genes 2 to 4-fold and with low penetrance alleles less than 1.5-fold. Overall, these factors account for about 25% of the genetic risk for breast cancer. In the remainder, genetic factors to contribute to the risk of breast cancer remain unknown and are a subject of current investigation. With discovery and validation of newer and clinically relevant predisposition factors, additional breast cancer risk categories may be recognized. BRCA1 and BRCA2 mutation testing allows identification of individuals at increased risk of breast cancer who are offered risk-reducing interventions. Targeted therapies are being developed that may refine management of patients with BRCA1 and BRCA2 mutations. Further genome-wide studies are required to identify clinically relevant molecular factors that will allow more accurate and widely applicable genetic risk stratification. Current efforts in discovery, validation and qualification of molecular markers of breast cancer risk offer considerable promise in the future to develop more accurate breast cancer risk assessment along with development of more effective chemopreventive and therapeutic strategies.