Results published in the Journal of the National Cancer Institute indicate that women with mutated BRCA1 or BRCA2 genes who undergo a bilateral prophylactic mastectomy significantly reduce their likelihood of developing breast cancer.
A gene is a hereditary unit of DNA that occupies a specific location on a chromosome (a linear strand of DNA and associated proteins in the nucleus of animal and plant cells). Genes carry instructions to cells telling them when and where to make specific proteins that perform and regulate all bodily functions. Genes replicate themselves during cellular division, but sometimes mistakes occur during replication. These mistakes are called mutations and may occur at random or in response to environmental factors. Mutations change the usual DNA sequence of a particular gene and may produce beneficial, harmful, or neutral results.
When children are conceived, they receive their genetic material from their parents. Because genes come in pairs, each parent contributes one copy of their own genes to their child. These copied genes will include any mutations located on the parent’s genome and as a result, the child will inherit these mutations. Current research suggests that only 5-10% of all cancers are inherited and the majority of breast cancer cases are not the result of known inherited mutations. However, researchers have identified two genes, that when mutated, are known to increase the risk of developing breast cancer: Breast Cancer Gene 1 (BRCA1) and Breast Cancer Gene 2 (BRCA2). The probability of developing breast cancer is only 12% in the general population, but jumps to 50-85% in women with inherited BRCA1 or BRCA2 mutations.
A bilateral prophylactic mastectomy is the surgical removal of both breasts prior to the development of cancer. Because it is such an invasive and extreme treatment, it has been highly controversial. Nonetheless, previous research of women with a family history of breast cancer has indicated that bilateral prophylactic mastectomy decreases the probability of developing cancer by up to 90%.
In a recent clinical study, American researchers examined the results of bilateral prophylactic mastectomy in 26 women with BRCA1 or BRCA2 mutations. None of the women had developed cancer 13.4 years after receiving prophylactic treatment. Computer analysis predicted that six to nine women carrying these mutations should have developed breast cancer, meaning that bilateral prophylactic mastectomy reduced risk of subsequent cancer by 89.5-100%.
These results demonstrate that women carrying BRCA1 or BRCA2 mutations who undergo a bilateral prophylactic mastectomy may reduce their risk of developing breast cancer by up to 100%. These results may assist genetic counselors who offer advice to patients regarding how best to interpret and respond to results of genetic tests. Individuals who are at an increased risk for breast cancer may wish to speak with their physician regarding the risks and benefits of genetic testing. More importantly, individuals who have confirmed BRCA1 or BRCA2 mutations may wish to speak to their physician about the risks and benefits of a bilateral prophylactic mastectomy or about participating in a clinical trial. Two sources of information regarding ongoing clinical trials include comprehensive, easy-to-use listing services provided by the National Cancer Institute (cancer.gov) and www.eCancerTrials.com. eCancerTrials.com also provides personalized clinical trial searches on behalf of patients. (Journal of the National Cancer Institute, Vol 93, No 21, pp 1633-1637, 2001)