Tuesday morning actress and sex symbol Angelina Jolie announced that she had both of her breasts removed in a preventative surgery to reduce her risk for breast cancer.
She did this because she has a mutation in a gene called BRCA1.
What's the risk?
Mutations in the BRCA genes (there are two, named 1 and 2 respectively) increase a person's risk for cancers, including breast and ovarian. Only about 0.25% of the general population has mutations in these genes.
While it's only a small amount of the population, someone who carries a mutation in one of these genes is much more likely than the average person to get cancer. A New England Journal of Medicine study indicates that having a mutated BRCA gene increases your lifetime risk of breast cancer to between 60 and 85%, and a lifetime risk of ovarian cancer between 15 and 40%, depending on the gene and the mutation.
The mutation is present in about 2% of female breast cancer cases and 10 to 15% of ovarian cancer cases.
Men with BRCA mutations are also at an increased risk for cancer, including male breast, pancreatic, and prostate cancers.
One dangerous mutation
Genes are the blueprint for the proteins that make up every cell of our body. They are made of a code of DNA letters, which sometimes are copied wrong, creating a mutation in the gene. When a gene is mutated, it may be unable to make a certain protein, which may result in health problems.
In the case of the BRCA mutations, the normal BRCA genes act as "tumor suppressors" — genes that protect cells from growing out of control and becoming cancerous. Unmutated BRCA genes help repair mistakes in genes that are commonly made when a cell multiplies and play a role in the "cell cycle" which regulates how quickly cells grow and multiply.
Therefore, a non-functioning BRCA gene could let tumors develop and also fail to prevent other cancer-promoting mutations.
Any given cell usually needs more than one mutated tumor-suppressor gene to become cancerous, however, which is why having one mutated BRCA gene isn't necessarily a death sentence.
Different mutations
Another important note on mutations in the BRCA genes — they aren't all the same. Not all mutations break the gene's protein product — and there is no definitive test to tell if you have a "working" BRCA gene.
In 10 to 15% of cases where doctors see a mutation in the gene they can't say whether it will break the gene and contribute to cancer risk.
In Jolie's case, however, her doctor reportedly said that her mutation carried a 87% risk of breast cancer and a 50% risk of ovarian cancer.
In such cases, preventative mastectomies are becoming more common — at least in Pennsylvania.
In 2002, 94 women in Pennsylvania had preventative surgery in which one or both of their breasts were removed either due to genetic factors or the presence of cancer in one breast. According to a 2012 study by the Pennsylvania Health Care Cost Containment Council, in 2012 that number was 455.
Note: We relied on the National Cancer Institute's wonderful, but very technical, summary of the Genetics of Breast and Ovarian Cancer for this post.
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