Various diseases have a genetic basis, such as risk factors that increase the probability of developing a certain disorder. Breast cancer is among these conditions.
Usually, breast cancer is not a hereditary disease. However, in a certain percentage of cases it has been shown to run in families. In these cases, many women who develop breast cancer show genetic factors that caused the disease – genes that increase the probability for cancer. It is estimated that around 5-10% of breast cancer result from genetic mutations.
There are two genes that increase the risk for breast cancer – BRCA1 and BRCA2. Among the populations at increased risk for BRCA mutations are women of Ashkenazi Jewish ancestry (Eastern European ancestry).
BRCA1, the more common of the two genes, causes a risk of around 80% for developing breast cancer. Women who are carriers of this gene variation are also at an increased risk of developing ovarian cancer (around five times higher than the risk in general population).
BRCA mutation carriers tend to develop the disease at an earlier age than in general population. Breast cancer linked to BRCA mutations is often triple-negative, which means that it is estrogen receptor negative and Her2 negative. This type of cancer tends to have a poorer prognosis. The defected gene can be inherited from one’s mother or father.
BRCA genes are linked to repairing damaged DNA. Since malignancies are related to genetic changes that create a loss of control over the division of cells, the connection between genetic defects and breast cancer is clear. However, the reason why these two types of cancer are at an increased risk remains unclear.
BRCA genetic testing
BRCA gene testing is recommended in several cases:
- A personal history of breast cancer and an extensive family history of this disease (or ovarian cancer)
- A history of breast cancer diagnosed at an early age (these cases tend to be linked to cancer with a genetic basis)
- A family history of BRCA gene carriers in close relatives
Since genetic mutations are found in all the body’s cells, this test is performed as a simple blood draw. Molecular testing uses PCR technologies to screen for common mutations in BRCA1 and BRCA2 genes.
Medical recommendations for BRCA mutation carriers
Medical recommendations for women who are BRCA mutation carriers are inconclusive. This raises many ethical and familial difficulties. On the one hand, being a carrier significantly increases the risk for developing breast and ovarian cancer.
On the other hand, many women prefer to not undergo these tests, if only during their period of fertility, out of fear of having to face difficult decisions in case of positive results. Is undergoing a double mastectomy worthwhile? At what age should one undergo this procedure? What about prophylactic ovary removal? These are difficult questions that do not always receive a clear answer from healthcare providers, and mostly remain subject a woman’s personal and religious beliefs.
BRCA carriers who choose not to undergo a double mastectomy must undergo frequent screening tests for an early and precise detection of cancer and a prompt treatment which can greatly affect their chances of recovery. Younger women are referred to MRI scans every six months (since mammography is less effective at a younger age), along with medical examinations and ultrasound scans.
Other genes linked to breast cancer
Besides BRCA gene variations, mutations in several other genes have also been found to be linked to an increased risk for breast cancer. These include the ATM gene (also related to correcting damaged DNA), P53, PTEN, CHEK2, and more.