While we don’t yet know exactly what causes most ovarian cancers, there are many ideas about this. Some of them come from looking at the things that change the risk of ovarian cancer. For example, pregnancy and taking birth control pills both lower the risk of ovarian cancer. Since both of these reduce the number of times the ovary releases an egg, some researchers think that there may be a link between the release of eggs and the risk of getting ovarian cancer.
Also, we know that women who have had their tubes tied (tubal ligation) or who have had their uterus removed (a hysterectomy) have a lower risk of ovarian cancer. One way to explain this is that some cancer-causing substances may enter the body through the vagina and pass through the uterus and fallopian tubes to reach the ovaries. This would explain why taking out the uterus or blocking the fallopian tubes might reduce ovarian cancer risk.
Another idea is that male hormones (androgens) can cause ovarian cancer.
A risk factor, like those mentioned above, is something that affects a person's chance of getting a disease. Different cancers have different risk factors. Some risk factors, such as smoking, can be controlled. Others, like a person's age or race, can't be changed.
But risk factors don't tell us everything. Having a risk factor, or even many risk factors, does not mean that you will get the disease. And many people who get the disease may not have had any known risk factors. Even if a woman with ovarian cancer has a risk factor, it is very hard to know what part that risk factor may have played in the development of the cancer.
Risk factors for ovarian cancer
Age: Most ovarian cancers happen after change of life (menopause). Half of all these cancers are found in women over the age of 63.
Obesity: Very overweight (obese) women seem to have a higher risk of getting ovarian cancer. A study from the American Cancer Society also found a higher rate of death from ovarian cancer in women who were overweight. The risk went up by 50% in the heaviest women.
Having children: A woman who has had children has a lower risk of ovarian cancer than women who have no children. The risk goes down with each pregnancy. Breast feeding may lower the risk even further. Using birth control pills ("the pill') also lowers the risk of ovarian cancer if taken for more than 5 years.
Female surgery: Having your "tubes tied" (tubal ligation) may reduce the chance of getting ovarian cancer. Removal of the uterus without removing the ovaries (a hysterectomy) also seems to reduce the risk of getting ovarian cancer.
Fertility drugs: Some studies have found that use of the fertility drug clomiphene citrate (Clomid®) for longer than one year, especially if no pregnancy took place, may increase the risk of low malignant potential tumors. But not having children also increases the risk, even without the use of fertility drugs. Research in this area is now going on. If you are taking this drug, you should talk to your doctor about the possible risks.
Male hormones: Androgens are male hormones. Women who took androgens were found to have a higher risk of ovarian cancer. Further studies are planned to look at this.
Estrogen therapy and hormone therapy: Some recent studies suggest women using estrogens after change of life (menopause) have an increased risk of ovarian cancer. The risk seems to be higher in women taking estrogen alone (without progesterone) for many years (at least 5 or 10). The increased risk is less certain for women taking both estrogen and progesterone.
Family history of ovarian cancer, breast cancer, or colorectal cancer: Ovarian cancer can run in families. Your ovarian cancer risk is higher if your mother, sister, or daughter has (or had) ovarian cancer. The risk gets higher the more relatives you have with ovarian cancer. Increased risk for ovarian cancer does not have to come from your mother's side of the family -- it can also come from your father's side.
Having a family member with breast cancer can increase your risk of ovarian cancer. And women who have colon cancer in their families may have a higher risk of developing ovarian cancer, too.
Many cases of familial epithelial ovarian cancer are caused by inherited gene mutations that can be identified by genetic testing. Please see the section, “Can ovarian cancer be prevented?” to learn about genetic counseling and testing.
Genetic changes and syndromes: Certain inherited gene changes (mutations) can increase the risk of ovarian cancer. These include changes in the BRCA1 and BRCA2 genes. If you have inherited a mutation of one of these genes from either parent, your chances of getting breast and/or ovarian cancer increase.
In some cancers, gene mutations may result from radiation or cancer-causing chemicals. But so far, studies haven't been able to link any single chemical in the environment or in our diets to mutations that cause ovarian cancer.
There are also several syndromes that increase the risk of ovarian cancer. A syndrome is a group of signs and symptoms that together point to a certain disorder or disease. The following syndromes increase the risk of ovarian cancer:
- Cowden's disease
- Hereditary nonpolyposis colon cancer (also called Lynch syndrome)
- Peutz-Jeghers syndrome
- MUTYH-associated polyposis
Breast cancer: Women who have had breast cancer also have a higher risk of ovarian cancer. The risk of ovarian cancer after breast cancer is highest in those women with a family history of breast cancer.
Talcum powder: Some studies have shown a slight increase in risk of ovarian cancer among women who used talcum powder on the genital area. Asbestos in the powder may explain the link. But these products have been free of asbestos for more than 20 years. Proving the safety of newer products will mean further studies of women who have used them for many years.
Diet: A study of women who followed a low-fat diet for at least 4 years showed a lower risk of ovarian cancer. Some studies have shown a reduced rate of ovarian cancer in women who ate a diet high in vegetables, but other studies disagree. The American Cancer Society recommends eating a variety of healthy foods. A healthy diet can help prevent other diseases, too, including some other types of cancer.
Smoking and alcohol use: These don’t increase the risk for most ovarian cancers, but some studies have found they increase the risk of one type (called mucinous). .
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