About 5% to 10% of breast cancers are thought to be hereditary, caused by abnormal genes passed from parent to child.
Genes are particles in cells, contained in chromosomes, and made of DNA (deoxyribonucleic acid). DNA contains the instructions for building proteins. And proteins control the structure and function of all the cells that make up your body.
Most inherited cases of breast cancer are associated with two abnormal genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two).
Everyone has BRCA1 and BRCA2 genes. The function of the BRCA genes is to repair cell damage and keep breast cells growing normally. But when these genes contain abnormalities or mutations that are passed from generation to generation, the genes don’t function normally and breast cancer risk increases. Abnormal BRCA1 and BRCA2 genes may account for up to 10% of all breast cancers, or 1 out of every 10 cases.
Having an abnormal BRCA1 or BRCA2 gene doesn’t mean you will be diagnosed with breast cancer. Researchers are learning that other mutations in pieces of chromosomes -- called SNPs (single nucleotide polymorphisms) -- may be linked to higher breast cancer risk in women with an abnormal BRCA1 gene as well as women who didn’t inherit an abnormal breast cancer gene.
Testing for abnormal BRCA1 and BRCA2 genes is usually done on a blood sample taken in your doctor’s office and sent to a commercial lab. During testing, the genes are separated from the rest of the DNA, and then they’re scanned for abnormalities.
Right now in the United States, Myriad Genetics performs all commercial BRCA1 and BRCA2 testing. Results are reported within a month. The cost of the BRCA testing ranges from about $300 to $3,000, depending on whether you get the limited test, in which only a few areas of the gene are evaluated, or the full test, in which hundreds of areas are examined on both genes.
A group of Canadian scientists has developed a new way to test for abnormal BRCA1 and BRCA2 genes that seems to be more accurate and less expensive than the current testing methods.
The research was published in the September 12, 2012 issue of the The Journal of Molecular Diagnostics. Read the abstract of “Long-Range PCR and Next-Generation Sequencing of BRCA1 and BRCA2 in Breast Cancer.”
The new BRCA testing method uses two relatively new techniques -- long range PCR and next generation sequencing -- to screen the entire genomic area of both genes. Because this new test can screen millions of DNA molecules at the same time, results are reported much faster -- in about 12 days -- and costs much less -- about $170 -- than the current BRCA1 and BRCA2 test.
The researchers ran their new BRCA testing method on blood samples from 12 people diagnosed with breast cancer who knew they had an abnormal BRCA1 or BRCA2 gene. The researchers then compared the results of the new test to the results from the current test. The new test found all the abnormal areas of the genes that the current test did, as well as several SNPs linked to breast cancer that weren’t identified by the current test.
While this research is very exciting, it will be some time before this new BRCA1 and BRCA2 testing is routinely available everywhere.
If you and/or some of your family members have been diagnosed with breast cancer, you may be interested in having genetic testing done. You’re much more likely to have an abnormal breast cancer gene if:
- You have blood relatives (grandmothers, mother, sisters, aunts) on either your mother’s or father’s side of the family who had breast cancer diagnosed before age 50.
- There is both breast and ovarian cancer in your family, particularly in a single person.
- There are other gland-related cancers in your family, such as pancreatic, colon, and thyroid cancer.
- Women in your family have had cancer in both breasts.
- You are of Ashkenazi Jewish (Eastern European) heritage.
- You are African American and have been diagnosed with breast cancer at age 35 or younger.
- A man in your family has been diagnosed with breast cancer.
If any of the items above are true for either side of your family, you may be a candidate for genetic testing. You may want to meet with a genetic counselor, a medical professional specially trained to understand and provide information about genetics and disease. To find a genetic counselor who specializes in family-related cancer risk, talk to your doctor or check with the hospitals and cancer centers in your area.
For more information on BRCA1 and BRCA2 testing, as well as other testing for other abnormal genes linked to breast cancer, visit the Genetics page in the Breastcancer.org Breast Cancer Risk Factors section.