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:

• the individual has personal or family history features suggestive of a genetic cancer susceptibility condition
  
  
• the genetic test can be clearly interpreted
  
  
• the results of the test will aid in the diagnosis or influence the medical or surgical management of the patient or family members with hereditary risk of cancer.

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:
  
  
  • Familial Adenomatous Polyposis (FAP)
  • Multiple Endocrine Neoplasia (MEN) 2A, 2B
  • Retinoblastoma
  • Von Hippel-Lindau (VHL)
    
    
• 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:
  
  
  • Hereditary Nonpolyposis Colon Cancer (HNPCC)
  • Hereditary Breast Ovarian Cancer Syndrome (HBOC)
  • Li-Fraumeni Syndrome
    
    
• 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:
  
  
  • Melanoma and melanoma-related syndromes
  • Ataxia Telangiectasia related susceptibilities

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.