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.
Reference materials:
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
