What is genetic testing?

Genetic testing looks for specific inherited changes (mutations) in a person’s chromosomes, genes, or proteins. Genetic mutations can have harmful, beneficial, neutral (no effect), or uncertain effects on health. Mutations that are harmful may increase a person’s chance, or risk, of developing a disease such as cancer. Overall, inherited mutations are thought to play a role in about 5 to 10 percent of all cancers.

Cancer can sometimes appear to “run in families” even if it is not caused by an inherited mutation. For example, a shared environment or lifestyle, such as tobacco use, can cause similar cancers to develop among family members. However, certain patterns —— such as the types of cancer that develop, other non-cancer conditions that are seen, and the ages at which cancer typically develops—may suggest the presence of a hereditary cancer syndrome.

The genetic mutations that cause many of the known hereditary cancer syndromes have been identified, and genetic testing can confirm whether a condition is, indeed, the result of an inherited syndrome. Genetic testing is also done to determine whether family members without obvious illness have inherited the same mutation as a family member who is known to carry a cancer-associated mutation.

Inherited genetic mutations can increase a person’s risk of developing cancer through a variety of mechanisms, depending on the function of the gene. Mutations in genes that control cell growth and the repair of damaged DNA are particularly likely to be associated with increased cancer risk.

Genetic testing of tumor samples can also be performed, but this Fact Sheet does not cover such testing.

Case

May 2013

Angelina Jolie's revealed that she had undergone a preventative double mastectomy after tests showed that she carries the BRCA1 cancer gene, leaving her with an 87% chance of contracting breast cancer.

March 2015

Now, two years later, Angelina has revealed she had her ovaries removed in a final procedure.

Angelina's family history
  • Brave actress Angelina, 39, lost her mum Marcheline Betrand to ovarian cancer.
  • Her cousin Francine, great aunt Stella and aunt Debbie died from breast cancer, and Grandad Rolland and uncle Raleigh also succumbed to different cancers.
  • Angelina's grandmother Lois died of ovarian cancer and her great-grandmother, Virginia, was killed by the same disease.

From website

Angelina's gene test result

She faced an 87% chance of developing breast cancer — about five times the general population risk — and a 50% risk of developing ovarian cancer.

Table : BRAC1/2 gene mutation carriers risk associated tumors
Tumour TypesRisk of ordinary peopleRisk of gene mutation
BRCA1BRCA2
breast cancer12%50~80%40~70%
secondary breast cancer3.5%~11% (5 years)27% (5 years)12% (5 years)
40~50% (20 years)
ovarian cancer1%~2%24%~40%11%~18%
ovarian cancer (Male)0.1%1%~2%5%~10%
prostate cancer15% (Nordic)
18% (Afro-American)
<30%<39%
pancreatic cancer0.50% 1~3%2~7%

Test Panel

Disclaimer : CCDB is an nonprofit resource available to genetics professionals to help them identify appropriate, currently available genetic tests. It assumes familiarity with the genetic mechanisms of disease causation and genetic counseling principles. Consumers are encouraged to speak with a healthcare provider or a genetics clinic for questions regarding availability and appropriateness of the recommended genetic testing.

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