Genetic Breast Cancer
There are some families that have a very high rate of women getting breast cancer. Until 1990, we did not understand these families. In 1990, the first of two genes were identified that when mutated caused a woman to have a very high risk of getting breast cancer. In 1994, the sequencing of this gene was completed and we could begin to sequence the gene in women to see if they had the mutation that placed them at high risk for getting breast cancer.The second gene,
BRCA2was discovered and sequenced in 1994 and 1995.
DNA plays an important role.
To date, most inherited cases of breast cancer have been associated with two genes: . The function of these genes is to keep
breast cells growing normally and to prevent any cancer cell growth. But when these genes contain
abnormalities, or mutations, they are associated with an increased breast cancer risk. Abnormal BRCA1 and BRCA2
genes may account for up to 10% of all breast cancers.
BRCA1, which stands
for BReast CAncer gene one, and
BRCA2, or BReast CAncer gene two
For a long time, many of us thought that breast cancer susceptibility was inherited through the maternal relatives. This is not the case with the mutations of the
BRCAgenes in women. These mutated genes can be inherited from either parent. Cases of breast and ovarian cancer may seem to skip a generation, when being carried by a male, but may well appear in females in the next generation. Remember,
breast cancer can occur in men, usually associated with a mutation of BRCA2.
Remember also that the gene is one complex area on a single chromosome and within that gene are multiple spots where alterations (mutations) can occur, over 200 in the BRCA1 and BRCA2 genes combined.
It is important that families with genetic breast cancer be identified. For women with a BRCA mutation, they will have a 70-85% lifetime risk of developing a single cancer and an elevated risk of developing ovarian cancer. If a woman has a breast cancer and a BRCA mutation, she may have as high as a 50% risk of developing a second breast cancer within the first 10 years after her first. If a family member has a BRCA mutation, her sisters and daughters will have a 50% of risk of inheriting the same mutation and having up to a 85% risk of developing their own breast cancer - sons and brothers will have the same risk of inheriting a mutation, but a much lower risk of developing a cancer.
Weighing the Cost of Testing Against the Possible Benefit of Diagnosis
There are already over 200 mutations identified on BRCA1 and BRCA2. When genetic testing is first done on material from a member of a high-risk family, the entire BRCA1 and BRCA2 genes may have to be examined to determine which one of the many mutations is present. This could cost $2500 or more. If a specific mutation is identified, then other family members can be tested for a considerably lower cost (less than $500) because the precise area to be analyzed is known. Such testing is not typically covered by health insurance policies.
The Importance of Counseling
When to Consider Genetic Cancer Counseling and Testing
Families should consider testing if they or a family member have:
- been diagnosed with breast cancer younger than 50
- diagnosed with ovarian cancer
- regardless of age, been diagnosed with breast AND ovarian cancer
- any male relative with breast cancer
- two or more relatives with breast or ovarian cancer
The closer the relationship with these relatives, the higher the probability that you might have a mutation. This is especially true for first degree relatives (parent, sibling, or child).
One note of caution -- even if you test negative against a panel of known mutations on a particular gene and don't have the bad mutation, you could still have a yet undiscovered mutation on that gene or on another gene that could increase your risk for cancer.