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From OncoLog, October 2013, Vol. 58, No. 10

Hereditary Cancers
Genetic screening can give valuable information

Graphic: House CallHereditary 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 genetic screening.

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 cancer.

Risk factors for hereditary cancer

Graphic: DNA

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 cancers:

  • 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

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

For more information, talk to your physician, visit www.mdanderson.org, or call askMDAnderson at 877-632-6789.

DNA simple2.svg: Forluvoft derivative work: Leyo (DNA simple2.svg) [Public domain], via Wikimedia Commons

Other articles in OncoLog, October 2013 issue:

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