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,

BRCA2

was discovered and sequenced in 1994 and 1995.

To date, most inherited cases of breast cancer have been associated with two genes:

BRCA1

, which stands for BReast CAncer gene one, and

BRCA2

, or BReast CAncer gene two. 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.

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

BRCA

genes 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.

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.

Far more important than cost is consideration of what the information from testing might mean and what effect it might have on a woman and on her family. Genetic testing of this sort is still in the research phase. Therefore, all physicians and health care professionals need to provide pretest and post-test counseling about what the potential results could be and what they mean, as well as support and follow-up for dealing with this knowledge. Expert counseling is crucial whenever genetic testing is undertaken.

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