What are the causes and risk factors for ovarian cancer ?
The risk factors for ovarian cancer are varied. Some of these factors are directly related to an individual’s constitution (constitutional factors), while others are linked to the environment (environmental factors). It is the interaction between constitutional and environmental factors that leads to the development of ovarian cancer.
Among constitutional factors, as with most cancers, age is a significant risk factor. The older a woman gets, the higher her risk of developing ovarian cancer: the risk peaks around the ages of 75-79, and the median age at diagnosis is 68 years (INCa 2019).
Another constitutional factor is heredity, which can play a role. Approximately 10% of ovarian cancers occur in the context of genetic predisposition. These hereditary forms are caused by mutations that are passed down from one generation to the next and contribute to cancer development.
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DNA is a set of 3 billion molecules that lie at the " core ," specifically in the nucleus of each of the 30 trillion cells that make up our body.
This DNA is composed of a sequence of four different elements named A, T, G, or C, based on the first letter of their full names. It forms a double helix and contains all the information required for the functioning of each cell.
This information is stored in small fragments of DNA called " genes ". There are approximately 21,000 genes that determine cell function and regulate the production of proteins, which are essential components of cells.
When cells divide, mutations can occur in the DNA, altering one or more elements within one or several genes. These mutations can be passed from a parent to a child ( hereditary genetic mutations ) or can occur spontaneously in an individual during their lifetime ( sporadic mutations ). Some mutations can increase the risk of developing cancers.
The two genes most frequently involved in the development of ovarian cancer are the BRCA1 (BReastCAncer 1) and BRCA2 (BReastCAncer 2) genes, which play an important role in DNA repair and controlling the growth of cancer cells.
The frequency of BRCA gene mutations varies between 19% and 31% according to studies. Patients with a mutation in the BRCA1 and BRCA2 genes have an increased risk of developing breast cancer, ovarian cancer, or both. The risk is much higher in the case of a BRCA1 mutation.
A patient with a BRCA1 mutation has about a 40% risk of developing ovarian cancer by age 50. In the case of a BRCA2 mutation, the risk is 10%, with the disease appearing around age 55.
However, mutations in these BRCA genes are rare in the general population, affecting about 1 in 300 people for the BRCA1 gene and 1 in 800 people for the BRCA2 gene. They are more common in certain populations, such as women of Ashkenazi Jewish descent: in this group, 1 in 40 women carries a BRCA gene mutation.
Other genes involved are the MMR (MisMatchRepair) genes, which contribute to DNA repair. When these genes are mutated, these mutations can lead to the development of a specific type of colorectal cancer, familial colorectal cancer without polyposis or Lynch syndrome, as well as the development of ovarian cancer, endometrial cancer (uterus), stomach cancer, small intestine cancer, or urinary tract cancers.
In addition to hereditary forms of ovarian cancer, there are also familial forms.
These can be due to genetic predisposition, lifestyle factors of family members, chance, or a combination of these various factors. The risk of ovarian cancer is higher in women whose first-degree relative (mother, sister, or daughter) has had ovarian cancer, particularly at a young age, or has developed breast cancer. A personal history of breast cancer is also a risk factor. These familial forms of cancer often appear at an earlier age, frequently before 50.
The duration of exposure to natural hormones throughout life is another constitutional factor. The longer this duration, the higher the risk. This exposure duration is defined by the period between the onset of menstruation and menopause.
The longer this duration and the more ovulations occur, as seen in cases of early puberty, late menopause, and lack of pregnancy, the greater the risk of ovarian cancer. Conversely, pregnancy, particularly multiple pregnancies, breastfeeding, and the use of oral contraception, have a protective effect.
Endometriosis, which affects one in ten menstruating women and is defined as the presence of tissue similar to the uterine lining outside the uterus, increases the risk of ovarian cancer.
Hormone replacement therapy (HRT) for menopause with estrogen or combined estrogen and progesterone increases the risk of ovarian cancer. Women who have undergone HRT for more than 5 years are at a higher risk of developing ovarian cancer than those who have used it for less than 5 years. Therefore, a treatment duration limited to 5 years is recommended, with an annual reassessment of its indication.
Among the environmental factors associated with ovarian cancers, the most proven is smoking. It increases the risk of a particular form of ovarian cancer, mucinous epithelial tumors, which represent 5 to 10% of epithelial cancers.
Obesity is also a risk factor. In France, it has been estimated that 5% of ovarian cancers are attributable to overweight and obesity (IARC, 2018).
Among occupational risk factors, asbestos has been recognized since 2009 as a definite carcinogen for the ovaries.
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Article updated on Jan 9, 2025
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