Is Hereditary Breast Cancer Common?
Genetic inheritance plays an important role in the development of breast cancer. About 10% of patients have inherited mutated genes. Patients with breast cancer gene mutations have a 10-fold higher chance of developing breast cancer. The most common genetic mutations in breast cancer occur in the BRCA 1 and BRCA 2 genes. When BRCA 1 & 2 mutates, it increases the risk of breast cancer or even other cancers, such as ovarian cancer and prostate cancer.
BRCA 1 & 2 gene mutations are inherited in an autosomal dominant manner, meaning if the child gets the abnormal gene from only one parent, the child will inherit the mutated gene and has a higher risk of getting cancer. Whether the BRCA gene mutation is found in a male or a female, it has a 50% chance of inheriting the BRCA 1 & 2 gene mutation to the next generation.
A Medical Guide That Keeps Pace with The Times
In consideration of the high cost of genetic testing in the past, previous international guidelines only recommended breast cancer patients who are most likely to directly benefit to undergo BRCA1/2 genetic testing. The threshold for genetic testing was set very high due to such costs. However, genetic testing technology has come a long way since, and testing costs have been greatly reduced. The ASBrS believes that the old guidelines may have led to many patients losing valuable genetic testing information and medical aid. Simply put, the old guidelines exclude, rather than include more patient rights. It is thus necessary to make updated recommendations in medical guidelines reflecting newer developments in genetic testing technology.
Why Do Those Already Diagnosed with Breast Cancer Still Require Further Genetic Testing?
More and more people understand that pre-emptive genetic testing for hereditary cancers (such as BRCA1/2 genetic testing) can allow people who have not yet developed a disease to know their risk of developing a certain type of cancer in their lifetime. Such high-risk patients can subsequently prevent and/or mitigate related cancers as early as possible, or undergo cancer screening more frequently such that cancer cells can be detected at an early stage of onset. Doing so will enable early medical interventions, which will improve treatment efficacy.
On the other hand, how can individuals who have already developed the disease benefit from genetic testing? According to guidelines issued by the ASBrS, the identification of genetic variants may affect doctors’ treatment recommendations for newly diagnosed breast cancer patients. For example, patients with BRCA gene mutations can be treated with PARP inhibitors, whilst patients with TP53 gene mutations should not be treated with radiotherapy to avoid inducing secondary malignant tumors.
Furthermore, about one in ten newly diagnosed breast cancers is correlated to genetic mutations. This means that this gene variant may also exist in relatives of the same family, and those who currently do not have the disease may be potentially high-risk for related diseases (for example, BRCA gene variants are not limited to women’s breast and ovarian cancer risks, but also increase men’s prostate cancer risk). Such gene mutations will also have a 50% chance of being passed on to the next generation.
Not Limited to BRCA1/2 Genes, But Also More Breast Cancer-Related Gene Variants
BRCA1/2 is the most common breast cancer gene mutation. With that said, in addition to the BRCA1 and BRCA2 genes, there are other breast cancer-related gene mutations such as CHEK2, PALB2, PTEN, RAD51C, RAD51D, STK11, and TP53 genes. The ASBrS strongly believes that individuals should consider genetic testing for hereditary breast cancer, including BRCA1, BRCA2, and PALB2 genes, as well as other genes suitable for the individual’s clinical situation and family history. Doing so will aid in better tackling medical complications, increasing treatment efficacy, and gaining a deeper understanding of potential health implications which may factor into family planning.
Manahan, ER, Kuerer, HM, Sebastian, M. et al. Consensus Guidelines on Genetic` Testing for Hereditary Breast Cancer from the American Society of Breast Surgeons. Ann Surg Oncol 26, 3025–3031 (2019). https://doi .org/10.1245/s10434-019-07549-8