DNA Testing for Cancer Susceptibility Genes
There are a growing number of genes being discovered that predispose
a person to developing cancer for which testing is available. Due to
the complexity of the testing and the issues surrounding testing, in
1996 the American Society of Clinical Oncology (ASCO) published
guidelines on when to offer cancer predisposition testing to patients.
ASCO recommended that cancer predisposition testing be offered only when:
- There is a strong family history of cancer or very early age
of onset of cancer.
- The genetic test can be clearly
interpreted.
- The results of the test will influence the
medical management of the patient with cancer or their family
members.
ASCO grouped hereditary cancers/cancer genetic testing into three categories:
Group 1
Families with a well-defined inherited cancer syndrome where the
genetic test result will affect medical care. Genetic testing is
considered part of the standard management of these families.
Syndromes include:
Group 2
Families with a well-defined inherited cancer syndrome where the
medical benefit of a person with a mutation in a cancer susceptibility
gene is presumed, but not proven. A positive test result may lead to
earlier surveillance or other cancer prevention. A negative test
result may greatly reduce the risk for cancer, or provide little
additional information. Syndromes include:
Group 3
Individuals without a family history of cancer or for syndromes
where germline mutations have been found in only a small number of
families, and for which the medical benefit of genetic testing is
unclear. Syndromes include:
ASCO concluded that testing should only be offered to persons in the
first two groups described above, in conjunction with the proper
education and counseling about cancer genetic risk factors.
Of note, ASCO also stated that cancer genetic testing should not be
offered to a person without a family history of cancer if the
significance of the detection of a susceptibility gene in that person
is not clear and for which the medical benefit is not apparent.