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Are you at risk for a certain disease? It's a question we've all pondered at
one time, says Brian Clark, Ph.D., M.D., director of the Cleveland Clinic Cancer
Center Medical Genetics Program. For some, the answer can be found within their
genetic heritage.
All genetic information is encoded in our genes and is inherited at
conception. Mutations in these genes may lead to inherited disease. For example,
while most cancers are sporadic—meaning they occur at random—5 to7 percent
of cancers of the breast, ovary and colon are due to an inherited gene defect.
Recent advances in the field of medical genetics have allowed breakthrough
findings for scientists—and new methods for physicians to test for certain
risks. This new technology allows patients to take action to safeguard their
personal health and the health of family members. Below, Dr. Clark discusses
what you should know about your personal risk for cancer.
Q: Under what circumstances should someone undergo genetic counseling and
testing?
A: For those with a family history of cancer, we recommend genetic
counseling as early as possible. For most individuals, that is at least age 18
or older.
Genetic counseling is helpful because it clarifies your individual risk for
cancer, and counselors can recommend ways to reduce your risk. For example, for
those with hereditary cancers, we recommend screening at an age that is at least
10 years younger than the earliest age a family member was diagnosed with
cancer. So if your mother was diagnosed with breast cancer at age 40, and your
sister was diagnosed with breast cancer at age 42, we would recommend that you
begin breast cancer screening at age 30 or younger.
The decision to undergo genetic testing for a specific disease is individual.
Some people undergo testing so they can use the information to make other life
choices, such as the decision to start a family and when, for example.
Q: How is the test performed?
A: Genetic testing involves a simple blood test. The test identifies a
change in a gene that is inherited from one of your parents. For breast and
ovarian cancer, the DNA of two genes is analyzed. It takes between three and
four weeks to get the result because the genes are analyzed piece by piece.
Under some circumstances, the process may be repeated two or three times.
Q: Can a positive test lead to early detection and aggressive disease
management?
A: Yes. If you test positive for a genetic mutation, you have several
options.
The first and easiest is increased cancer surveillance. Discuss with your
doctor the appropriate intervals for future screenings.
The second option is chemoprevention. This involves taking medications that
may prevent a cancer from developing. Many women at high risk for developing
breast cancer are taking Tamoxifen as a prevention strategy, for example.
The third, and most drastic, option is prophylactic surgery. For example, in
order to prevent breast cancer, some high-risk women may choose to have their
breasts removed before breast cancer develops. Studies show that undergoing
prophylactic mastectomy does prevent the disease.
Remember that not all cancers develop from an inherited gene mutation. Many
diseases occur randomly or as a result of external exposure or lifestyle risk
factors, such as smoking. Discuss with your doctor which screening tests are
appropriate for you and when.
Q: How does genetic testing complement traditional cancer screening?
A: The purpose of genetic testing is risk stratification. In other words,
genetic testing can identify you as either high risk for developing the disease
or low risk.
If your mother had an inherited breast cancer syndrome, you have a 50 percent
chance of inheriting it. If you test positive for the syndrome after genetic
testing, your lifetime breast cancer risk approaches 85 percent. If you test
negative, your risk approaches that of the general population.
Q: Have we entered a new era of medical genetic sleuthing?
A: In some sense, we have. However, this new era offers both advantages
and disadvantages for the patient.
The great promise lies in the development of a genetic profile of diseases,
such as diabetes or hypertension, to which a person might be predisposed. Thus,
if we know we fit a particular profile, we can take our diet and exercise more
seriously, and physicians may be able to individually tailor diagnostic and
treatment methods more effectively.
The downside is that not all of us may wish to be labeled as someone who is
predestined to have a heart attack or colon cancer, for example.
Overall, though, the knowledge that you may be at high risk for certain
diseases can be a powerful motivator that may lead to better health habits and
regular health screenings—your best defenses against disease.
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