About 80 percent of breast cancer patients have no family history of breast cancer. Their cancers are called “sporadic” breast cancers. Another 15 to 20 percent of breast cancer patients have some family history of breast cancer, called “familial” breast cancer, that may indicate a genetic susceptibility.
Between 5 and 10 percent of breast cancer patients have a very strong family history of breast cancer. Their cancers are considered “hereditary.” This term could apply to the occurrence of breast cancer in closely related family members on one side of the family across generations: for example, breast cancer in a combination of one’s mother, aunt, daughter, grandmother, and great aunt. It could also apply to more than one occurrence of early-onset (under age 50) breast cancer or the incidence of cancer in both breasts in an individual family member; or to the presence of male breast cancer in the family.
Mutations in two particular genes — named BRCA1 and BRCA2 — account for most hereditary breast cancers. To illustrate the power of these mutations, consider these statistics: The general population has a 7 percent chance of getting breast cancer; those with the BRCA1 and BRCA2 mutations have a 55 to 87 percent chance. Risks for some other types of cancer also increase for those with either gene mutation, male or female.
Although genetic, or gene, testing can be done on a sample of blood obtained the same way as for the diagnosis of illness or for routine blood work-ups, much thought and discussion with one’s oncologist and a genetic counselor on his or her professional team should precede testing because of the complicated DNA testing process that is done only at specialized medical laboratories and its resulting high cost.
Testing results are considered very reliable. A genetic counselor is specially trained to understand and explain the statistical probabilities that can be derived from testing and clarify the result obtained, because it isn’t as simple as “you have it” or “you don’t have it.” It is one of four possibilities: positive, ambiguous, or one of two types of negative. Along with a personal consultation, the genetic counselor uses simple graphs, charts, and layman’s terms to make the process understandable.
Genetic testing should be done with a willing family member who has already been diagnosed with breast cancer, because she is most likely to have the mutated gene if one exists. She should first contact her health insurance company to see if some of the costs of testing are covered by her policy, because it is quite expensive. If testing is done and either mutation is found in her DNA, any follow-up testing for family members is a simpler and less costly process.
If a mutation is found, the only conclusion that can justifiably be drawn is that family members are at increased risk. A positive result does not make breast cancer inevitable, but it does allow decisions to be made about more frequent screening, the addition of advanced screening methods, preventive surgery options, or preventive drug treatment. A negative result can bring reassurance to family members that their — and their daughters’ and granddaughters’— chances of getting breast cancer are no greater than those of the general population. Adult daughters and granddaughters should only be given test results, however, if they want to know them because of the Pandora’s Box that can be opened as a result of knowing. All genetic testing decisions are very personal, and should be the individual’s choice.
All 50 states have laws protecting those who undergo genetic testing from having their results used as evidence of a pre-existing condition. Protection is also offered by the Health Insurance Portability and Accountability Act and the Americans with Disabilities Act of 1990. There are a few exceptions, however, which bear investigation before testing is done.
Although BRCA1 and BRCA2 mutations are the first to be identified, researchers are working hard to uncover other cancer-related gene mutations.