Breast cancer, genetic testing

With the advent and ensuing media coverage of Angelina Jolie’s prophylactic breast cancer surgery, the interest of the general population has now been piqued and many are wondering about breast cancer and genetic testing.

Breast cancer is one of the most common cancers among American women, second only to skin cancers.  It occurs in about twelve percent or one in eight women.  However, individuals who have inherited a BRCA1 or BRCA2 gene mutation are five times more likely to develop breast cancer in their lifetime.  

So what are BRCA1 and BRCA2?  These designations stand for breast cancer susceptibility genes 1 and 2.  They are human genes that belong to a class of genes known as tumor suppressors.  These genes code for proteins that are responsible for repairing broken DNA and maintaining the stability of cell growth.  If the genes are altered, i.e. mutated, they cannot properly produce the necessary protective proteins to fix faulty DNA.  Faulty DNA can lead to abnormal cell growth or cancer cells.

Certain individuals can inherit a harmful BRCA mutation.  The likelihood of inheriting a mutated BRCA gene is highest in women who have a family history of multiple cases of breast and ovarian cancers and among certain ethnicities, such as Ashkenazi (Central and Eastern European) Jewish, Norwegian, Dutch, and Icelandic backgrounds. 

However, it must be stressed that not every woman in such families has a mutation in one of the genes and not every woman who has a harmful BRCA1 or BRCA2 gene will develop breast cancer.

Genetic testing can be performed to determine if an individual has inherited one or both of these gene mutations.  The testing involves drawing a blood sample and examining either the BRCA DNA directly or looking for changes in the proteins produced by these genes.  Counseling with a cancer geneticist is recommended before and after testing.

Determining who should be tested for the mutations is the big question.  Information should first be gathered regarding an individual’s personal and family health history- a risk assessment.  Because no diagnostic test is completely 100 percent  accurate, there may be false positive tests and false negative tests.  This can lead to undo anxiety regarding the results.  Generally, it is more informative to test individuals in the family who have been diagnosed with breast or ovarian cancer to see if they have the mutation.  If they test positive for the mutation then it is more appropriate that other members of the family also be tested.

If a harmful BRCA mutation is found in an individual, several management options are available; these include continued cancer screening (regular mammograms and clinical breast examinations), prophylactic mastectomy, and medications that can reduce the risk of developing cancer.  However, high-quality data as to the overall effectiveness of each of these options in preventing cancer is still being developed.

Breast cancer can also develop in people who do not have BRCA1 or BRCA2 mutations.  Other risk factors that show some association with getting breast cancer include advancing age; family history of a first-degree relative with breast cancer; a personal history of breast cancer; hormone therapy; obesity; lack of physical activity; alcohol consumption; and a diet high in fat.  

The content in this column is for informational purposes only.  Consult your physician for appropriate individual treatment.  Dr. Reynolds practices Family Medicine in Chesterfield.


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