What is a gene?
The genetic material called DNA present in the nucleus of human cells contains small fragments called genes. These genes decide the individual traits like color of hair, skin & eyes etc. Each person has two copies of every gene, one gene from each parent. There is a 50% chance of the parent’s trait being passed on to their offspring as each parent passes down exactly half of their genes to each child.
What is BRCA?
The term “BRCA'' is an abbreviation for “BReast CAncer gene.”
Every human has both, BRCA1 and BRCA2 genes which function normally in order to prevent development of breast cancer by producing proteins that help in repairing DNA breaks.
Thus, these genes are known as tumor suppressor genes.
BRCA mutation & breast cancer
A gene is said to be mutated, when it becomes altered or broken. This mutation hampers the function of the gene.
When the BRCA gene gets mutated, it is no longer effective at repairing broken DNA and helping to prevent breast cancer. Thus, people with a BRCA gene mutation are at risk of developing breast cancer. These mutated genes can also be passed on to the next generation. If one of the parents has a BRCA mutation, the offspring has a 50% chance of inheriting the mutated gene. Approximately 45% of women with a BRCA2 mutation will develop breast cancer by age 70.
There is a high risk for BRCA mutations if there is a family history of:
- Breast cancer diagnosed before age 50.
- Male breast cancer at any age.
- Family history of breast cancer, particularly the first-degree relatives (mother, sister, daughter).
- Multiple breast cancers in the same woman, meaning breast cancer developing in both breasts over time or at the same time.
- Co-existing breast and ovarian cancer in the same woman.
- History of ovarian cancer in the woman’s family, especially if a first-degree relative.
- Ashkenazi Jewish heritage.
Inheritance of the BRCA gene
https://en.wikipedia.org/wiki/BRCA_mutation#/media/File:Autodominant_en.svg
BRCA mutation & other cancers
https://en.wikipedia.org/wiki/BRCA_mutation
Other cancers associated with the BRCA mutation are fallopian tube cancer, peritoneal cancer , ovarian cancer. Men with BRCA mutations are also at increased risk of breast cancer and prostate cancer. Both men and women with harmful variants of BRCA1 & BRCA2 are also at increased risk of pancreatic cancer .
Screening for BRCA mutated genes
The screening for these mutated genes is targeted towards those who have a higher likelihood of carrying a harmful BRCA1 or BRCA2 variant, such as those who have a family history of certain cancers.
Two types of tests are available both of which use a blood sample, although saliva can be used for testing. The test is ordered by a physician, usually an oncologist, and the results are always informed to the physician, rather than directly to the patient.
This information can help these individuals to take steps to reduce their risk or detect cancer early which can lead to better prognosis. It also plays a role in selecting the treatment.
Interpretation of BRCA results
- A negative result means no BRCA gene mutation, but it doesn't mean one would never get cancer.
- An uncertain result means some kind of BRCA gene mutation, but it may or may not be linked with an increased cancer risk. Further tests and/or monitoring may be required.
- A positive result means a mutation in BRCA1 or BRCA2. These mutations put an individual at a higher risk of getting cancer. But not everyone with the mutation gets cancer.
Benefits of genetic testing
Genetic testing may help in seeking medical and lifestyle decisions and easing the anxiety. One can also decide regarding prevention, with both medications and prophylactic surgery. Also, many women take part in medical research that, in the long run, may lower their risk of death from breast cancer.
References:
- Eccles, B.K., Copson, E., Maishman, T., Abraham, J.E. and Eccles, D.M., 2015. Understanding of BRCA VUS genetic results by breast cancer specialists. BMC cancer, 15 (1), pp.1-9.
- Forbes, C. et al. (2019) ‘A systematic review of international guidelines and recommendations for the genetic screening, diagnosis, genetic counseling, and treatment of BRCA-mutated breast cancer’, Cancer Management and Research, 11, p. 2321. doi: 10.2147/CMAR.S189627.
- Lee, M. V. et al. (2017) ‘BRCA-associated cancers: Role of imaging in screening, diagnosis, and management’, Radiographics, 37(4), pp. 1005–1023. doi: 10.1148/RG.2017160144/ASSET/IMAGES/LARGE/RG.2017160144.FIG15D.JPEG.
- Lippi, G., Mattiuzzi, C. and Montagnana, M. (2017) ‘BRCA population screening for predicting breast cancer: for or against?’, Annals of Translational Medicine, 5(13). doi: 10.21037/ATM.2017.06.71.
