Genetic screening can give valuable information
Hereditary cancer—cancer that is passed down from generation to
generation—accounts for 5%–10% of all cancer cases. Many of these
cancers are caused by hereditary syndromes that can be detected by
Common hereditary cancers include those caused by hereditary breast and
ovarian cancer syndrome and hereditary nonpolyposis colorectal cancer
syndrome (Lynch syndrome). People who are at risk for hereditary
cancers may be offered additional screening or treatment to help detect
or prevent cancer. Patients who have cancer that has been diagnosed as
hereditary may benefit from adjusted treatments or screening to help
prevent additional cancers or detect them early.
To determine a healthy person’s likelihood of developing hereditary
cancer or to find whether an existing cancer is hereditary, genetic
counselors and doctors assess the person for several risk factors.
Depending on the risk factors a person has, a genetic counselor may
recommend genetic testing to diagnose an existing cancer as hereditary
or to further assess a healthy person’s likelihood of developing
Risk factors for hereditary cancer
Genetic counselors assess a person’s family history and personal
history of cancer to determine his or her risk for one or more
hereditary cancers. Knowing about a high risk for a hereditary cancer
allows a person to take steps to reduce the chances of developing that
cancer. The following groups may be at risk for one or more hereditary
- People who have multiple relatives with the same
type of cancer. A family history of cancer is often the strongest
predictor of hereditary cancer. However, given that 30%–40% of people
have cancer at some point in their lives, a family may have a history
of cancer that appears to be hereditary but is not. Genetic counselors
can determine whether a pattern of cancer in a family is likely to
signal a hereditary cancer.
- Patients who have or have had multiple types of
cancers. Some hereditary genetic changes increase a patient’s risk for
developing multiple cancers. Thus, having multiple cancers is a strong
indicator of a hereditary cancer syndrome. For example, patients who
have the most common form of hereditary breast cancer are likely to
develop ovarian cancer, too.
- Patients who developed cancer earlier in life than
other patients who have the same type of cancer. Hereditary cancer
often develops earlier than the same type of nonhereditary cancer.
People who suspect they are at risk for hereditary cancers should ask
their doctors about meeting with a genetic counselor who can assess
whether genetic testing is appropriate.
Genetic testing can be valuable for people with or without cancer.
“Genetic testing clarifies the risk for cancer or an additional cancer
for the patients and their relatives,” said Thereasa Rich, M.S., a
genetic counselor in the Clinical Cancer Genetics Program at The
University of Texas MD Anderson Cancer Center. For people with a
personal history of cancer, genetic testing is used to diagnose their
cancer as hereditary or not. For healthy people with a family history
of cancer, genetic testing is used to find out if they have genetic
changes that could lead to hereditary cancer.
Genetic testing is used to identify mutated genes that can cause
cancer. “These genes are well studied and well known, and they have
published guidelines and recommendations for how to interpret the
results,” Ms. Rich said. For example, people with a mutation in the
BRCA1 or BRCA2 gene have an increased risk for breast cancer, ovarian
cancer, and other cancers. Parents who have a mutated gene have a 50%
chance of passing it to their child.
Certain criteria must apply before a counselor will recommend genetic testing:
- The person must be at risk for a hereditary cancer
for which a genetic test is available. (Currently, genetic tests are
not available for every type of hereditary cancer.)
- Positive results of the genetic test must change
the course of treatment or screening. For some cancers, the recommended
treatment or screening procedure may be the same for people with
positive and negative results.
- The person must voluntarily agree to genetic testing and be able to handle the stress of the result.
Genetic testing is not often recommended for people whose family
history and personal history suggest a low risk for hereditary cancer.
Not all people found to have genetic mutations that increase the risk
for hereditary cancer will develop the disease. “It is an imperfect
test that needs to be interpreted in a broader context,” Ms. Rich said.
“Make sure you are counseled about what the results might mean.”
— C. Wilcox
information, talk to your physician, visit www.mdanderson.org, or call askMDAnderson at 877-632-6789.
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articles in OncoLog, October 2013 issue:
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