Breast cancer is quite common in Greece with an annual number of cases reaching around 4000 – 4500. The number of breast cancer cases is equally high among women of other countries. This urged scientists to study this type of cancer in detail, to develop tests for early detection and treatment options. It has be defined that the genes responsible for the development of breast and ovarian cancer are BRCA1 and BRCA2.
Inherited forms of breast and ovarian cancer
The human genes BRCA1 and BRCA2 belong to a group of genes known as tumour suppressors. In their natural state these genes are responsible for the stability of the DNA, preventing irregular growth. Mutations on these genes have been linked with inherited forms of ovarian and breast cancer. The possibility of a woman of developing breast or ovarian cancer is increased if she has inherited a mutation on one of the genes. In a much less extent, men who have inherited the mutated BRCA1 and BRCA2 genes have a chance of developing breast cancer. The risk of developing other types of cancer is increased in men and women with the mutated forms of BRCA1 and BRCA2. However, it is important to highlight that not all men or women with mutations on the genes will develop cancer. Around 55-65% of women with BRCA1 mutations will develop breast cancer and 39% will develop ovarian cancer. Amongst women with BRCA2 mutations 45% will develop breast cancer and 11 to 17% will develop ovarian cancer .
There are tests available that help in early detection of mutation on BRCA1 and BRCA2 providing time for the most suitable course of treatment. This test should be offered in women:
- With breast cancer history in at least two first-degree relatives (mother, daughter, sister) who suffered with the disease at an age less than 50 years.
- With breast cancer history in three or more first or second-degree relatives (grandmother, aunt) regardless of age of diseases onset.
- With breast and ovarian cancer history in first and second-degree relatives.
- With history of cancer in both breasts (bilateral) in a first-degree relative.
- With history of ovarian cancer in two or more first and second-degree relatives regardless of age of onset.
- With history of breast and ovarian cancer (occurring together) in one first or second-degree relative, regardless of age of disease onset
- With history of breast cancer in a male relative.
The positive result of the test for BRCA1 or BRCA2 mutations suggest that the woman has increased chance of developing some forms of cancer mainly breast and/or ovarian. The presence of the mutation will not necessarily lead to the cancer, nor that the children these women have will necessarily develop cancer themselves. In cases of absence of any mutation the risk for developing cancer is reduced but not eliminated. The risk of developing breast cancer in individuals without the mutation is the same as that of the general population.
People that carry the mutated forms of BRCA1 or BRCA2 should:
- Be under close observation with mammograms, colposcopy, clinical tests and blood tests for the CA-125 antigen.
- Prophylactic mastectomy or removal of the ovaries. This however, does not eliminate the risk of the development of cancer.
Breast cancer in the general population
There are some factors that favors the development of breast or ovarian cancer in the general population, like:
Age. This risk of developing breast and/or ovarian cancer increased with age especially after 50 years old. Women carrying the mutated BRCA1 or BRCA2 genes may develop cancer before the age of 50.
- Family history. Women with first-degree relatives or other close relatives that have suffered breast and/or ovarian cancer have increased risk of developing these forms of cancer.
- Medical history. Women who have already went through breast cancer have an increased risk of developing either breast or ovarian cancer.
- Hormonal influences. Estrogen is a hormone that is created naturally by the woman’s body. It is believed that increased estrogen production may increase the risk of breast cancer development. Women whose cycle started before the age of 12 or had their menopause after the age of 55 have a slightly increased risk of breast cancer development. This is valid also for women that had their first child before the age of 30. On the other hand, the removal of the ovaries, which is the main source of estrogen, as well as breast-feeding decrease the risk of cancer development.
- Contraceptive pill. Many studies have shown that there is a slight increase of cancer development in women that take the contraceptive pill.
- Hormone replacement therapy (HRT). Many women choose HRT as their doctor suggests in order to reduce the menopausal symptoms. Studies performed by the National Institutes for Health in the States showed that hormonal replacement with the combination of estrogen and progesteron cases important side effects like increased risk developing breast cancer, heart arrack and stroke. Hormonal replacement using only estrogen may cause heard attach or stroke but its effect on increasing the risk for breast cancer development has not been confirmed. For this reason the hormonal replacement should be mild and for a small period of time. Not many studies exist on the effect of hormonal replacement in women who carry a BRCA1 or BRCA2 mutation.
- Obesity. There are a lot of indications that obesity is linked with increased risk of breast cancer development, especially in menopausal women and with increased death rate among obese women with ovarian cancer.
- Physical exercise. Many studies have shown that intense physical exercise reduces the risk of cancer development especially in women that are not menopausal or those with less than average weight.
- Alcohol. There are important indications that excessive alcohol consumption is linked to increased risk of breast cancer.
- Chen S, Parmigiani G. (2007). Meta-analysis of BRCA1 and BRCA2 penetrance. Journal of Clinical Oncology. 25(11): 1329-1333.