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About 30 percent of breast and ovarian cancers result from a strong genetic predisposition, which means that the cause of the disease is mutations in the genes. From an ordinary blood sample taken from the clinic and sent to a specialized laboratory, geneticists can read our future and close it in indicative numbers – this may scare, but also give a chance for health. What do our genes say about breast cancer and ovarian cancer?
As an introduction
For most of us, being aware of genetics comes down to surprise that a pair of brunettes can have a fair-haired baby. Those interested in genetics can use Mendel’s law to figure out the secret of the eye color of a fruit fly. Mutations, i.e. damage that disrupts the proper functioning of genes, can be inherited from generation to generation. There are single-gene and multi-gene inheritance. In the first case, a mutation in a single gene predisposes to a malignant tumor (remember that a damaged gene is found in every cell of the body!). In families with such a mutation, the risk of developing the disease is high and reaches about 50%. Multi-gene inheritance is more complicated because many genetic factors (and not a single gene as in monogenic inheritance) are responsible for the development of a malignant neoplasm. The risk of developing the disease among family members is small, usually one person is ill.
BRCA1 i BRCA2
A strong genetic predisposition to developing breast cancer (both in women and men!) And ovarian cancer is associated with mutations in two genes: BRCA1 and BRCA2. In short, these genes are responsible for the repair processes of DNA. Their mutation causes the damage to the DNA chain to be left alone and the number of defective chromosomes increases, which in turn promotes the development of the neoplastic process.
Detection of mutations in the BRCA1 or BRCA2 gene means a very high risk of breast cancer and / or ovarian cancer. Depending on the source, it is assumed that in women with one of the mutations, the risk of developing breast cancer is 30-80%, ovarian cancer from about 11% to about 40%, and for tubal and peritoneal cancer about 10%. This risk probably depends on the type of mutation and its location in the gene.
What is very important: only about 3% of all cases of breast cancer and about 14% of all cases of ovarian cancer are caused by a mutation in the BRCA1 gene! So far, there are no statistical data on the carrier of the BRCA2 gene mutation in the Polish population and its influence on the risk of breast and / or ovarian cancer.
The vast majority of cancers are so-called sporadic neoplasms, which do not carry an increased risk of disease by family members. Therefore, it is not necessary to subject all people suffering from these cancers to genetic testing. Premises that may indicate the genetic basis of the disease are indicated on the basis of a family interview by the attending physician, and it is he who refers the patient for tests.
The alarming signal for the possible occurrence of the BRCA1 mutation in the family is the large number of breast and / or ovarian cancers, and for the BRCA2 mutation also male breast cancer!
Prevention
In the case of burdening any of the mutations, unfortunately, the most effective are radical measures, i.e. prophylactic mastectomy and / or adnexectomy, i.e. amputation of the ovaries and appendages.
There is a lack of data indicating the extent to which prophylactic mastectomy protects against breast cancer, in one study American researchers estimate it to be a high 90 percent risk minimization rate. Polish authors of the work entitled Hereditary breast and ovarian cancer inform about single (1%) neoplasms developing e.g. in the chest wall despite breast amputation, but suggest leaving this possibility to patients at the highest risk, e.g. those in whom the structure of the mammary glands hinders early diagnosis using mammogram. Preventive mastectomy is usually performed simultaneously with immediate breast reconstruction surgery, which significantly improves the patient’s psychological comfort.
Prophylactic adnexectomy, often supported by hormone replacement therapy, also gives the expected results (the risk of ovarian cancer drops to 5%, and breast cancer risk to 30-40%), so it is recommended to perform the procedure in all women with BRCA1 / 2 gene mutation that have exceeded 40 year of life. According to the data of the International Hereditary Cancer Center in Szczecin, 85% of patients agree to this form of therapy.
In prophylaxis and therapy, the so-called chemoprevention by taking an anti-estrogen drug called tamoxifen. This specificity reduces the risk of breast cancer by up to 50%, but sources indicate its serious side effects, such as osteoporosis, cardiovascular disease and premature menopause.
The question of taking oral hormonal contraceptives by women burdened with the BRCA1 / 2 gene mutation is controversial. There are known contraindications for patients under 25 years of age. Later in age (over 30) the pills reduce the risk of developing ovarian cancer by up to 1% in patients with a BRCA50 mutation and do not appear to increase the risk of breast cancer. In addition, it is recommended to breastfeed as long as possible – a total of 18 months of breastfeeding reduces the risk of breast cancer by about 50%, i.e. up to 25%.
People with a detected mutation of any of the genes and their families are, of course, covered by the preventive care of oncological specialist centers.
Treatment and prognosis
Breast and ovarian neoplasms caused by mutations in the BRCA1 gene differ from sporadic neoplasms. Such tumors grow rapidly, often showing a high degree of malignancy when detected, and their biochemical structure is also different. That is why it is so important to diagnose genetic mutations, because it allows for individualized and adapted to a specific case therapy. This is especially important when mutating the BRCA1 gene.
Patient survival studies were carried out, inter alia, among Ashkenazi Jews burdened with the discussed mutations. They showed that despite the different histopathological features of tumors caused by these mutations, their carriers have the same prognosis as those suffering from sporadic tumors.
So what does the awareness of the mutation burden mean for the patient?
– The large numbers determining the risk of cancer are certainly shocking for patients with a detected mutation in the BRCA1 or BRCA2 gene. The risk is high and under no circumstances should the test result be underestimated, but it should be remembered that just as a negative genetic test result does not guarantee health, a positive result is not an irrevocable prediction of the disease ahead. In patients at high risk, genetic tests, also carried out in their families, are highly recommended because this knowledge, although shocking for the patient, gives the doctor new possibilities of prevention and treatment. The prevention program allows you to keep your finger on the pulse and intervene immediately if necessary, and individualization of therapy is one of the key issues leading to a cure. – says Dr. Dariusz Godlewski from the Center for Prophylaxis and Epidemiology of Cancer OPEN in Poznań.
Julia Wolin
medical consultation: Dr. Dariusz Godlewski from the Center for Prophylaxis and Epidemiology of Cancer OPEN in Poznań
Read more in What should you know about breast screening?
BIBLIOGRAPHY:
Principles of inheritance of cancer predisposition. Tadeusz Dębniak, Jan Lubiński
Hereditary cancer of the breast and ovary. Jacek Gronwald, Tomasz Byrski
Press releases and the actual possibilities of genetic counseling in the psycho-oncological aspect.