Gene screening involves a comprehensive evaluation of breast carcinoma using a pathology supported genetic testing (PSGT) approach to define cancer subtypes, predict disease recurrence and guide treatment decisions.
What is breast cancer? All breast cancers are caused by genetic abnormalities (mutations), which are either inherited or acquired:
- An inherited genetic abnormality can be passed on from a parent to a child (male or female), who has a 50% chance of inheriting the faulty gene (and a 50% chance of inheriting the normal copy of the gene).
- An acquired (or non-hereditary) genetic abnormality is caused by an error during gene reproduction or from interaction with environmental factors such as hormonal influences, toxic exposure or an inappropriate diet.
Acquired genetic abnormalities account for more than 80% of breast cancers. Mutations in the BRCA1 and BRCA2 genes are the best-known cause of inherited breast cancer, but explain less than 5% of the total breast cancer incidence and approximately 20% of cases with a family history of breast cancer. A large proportion of familial breast cancer is caused by the cumulative effect of multiple inherited abnormalities that interact with each other and the environment to increase cancer risk. The influence of other cancer-related genes may also explain why some patients with a BRCA1 or BRCA2 mutation develop breast, ovarian or other forms of cancer at a relatively young age, while other family members with the same mutation remains healthy throughout life.
In their normal form, the BRCA1 and-2 genes prevent breast cancer by producing a protein that control cell growth. When someone inherits a BRCA1 or -2 mutation from his or her mother or father the cell will still function normally if the normal gene copy inherited from the other parent is working properly. However, when the normal BRCA gene breaks down, for whatever reason, both copies of the gene are now abnormal and it can no longer control cell growth to prevent cancer. When breast cells multiply at a rate much higher than normal, some can invade healthy tissue and cause invasive breast cancer. This form of cancer differs from non-invasive cancer where cells also grow uncontrolled, but have not started to invade the normal surrounding healthy tissue.
In addition to diagnostic applications, several genetic tests became available during recent years for breast cancer prognosis and prediction of treatment response.
Identification of genetic abnormalities may form the basis of intensified surveillance programs and personalized treatment programs.
Genetic counseling is important to determine the appropriateness of genetic testing based on family history (e.g. BRCA1/2), pathology (e.g. MammaPrint) and environmental factors that may influence treatment response at the pharmacogenetics/nutrigenetics interface.