The American Cancer Society defines a risk factor as anything that increases a person's chance of getting a disease such as cancer. According to ACS, different cancers have different risk factors. For example, unprotected exposure to strong sunlight is a risk factor for skin cancer, and smoking is a risk factor for lung cancer. According to the American Cancer Society, researchers have discovered several specific factors that increase a woman's likelihood of developing epithelial ovarian cancer. These risk factors do not apply to other less common types of ovarian cancer such as germ cell tumors and stromal tumors.
Most women with ovarian cancer do not exhibit any known risk factors. It is important to remember that risk factors increase the odds of getting a disease, but do not guarantee it will occur. Only a small number of women who have risk factors will develop ovarian cancer.
Aging: Most ovarian cancers develop after menopause. A woman is considered to be menopausal when she has gone a year without a menstrual period. Half of all ovarian cancers are found in women over the age of 65.
Reproductive History: Women who started menstruating at an early age (before age 12), had no children or had their first child after age 30, and/or experienced menopause after age 50, may have an increased risk of ovarian cancer. There seems to be a relationship between the number of menstrual cycles in a woman's lifetime and her risk of developing ovarian cancer.
Fertility Drugs: In some studies, researchers have found that prolonged use of the fertility drug clomiphene citrate, especially without achieving pregnancy, may increase a woman's risk for developing ovarian tumors, particularly a type known as tumors of low malignant potential (LMP tumors). A woman taking this drug should discuss its potential risks with her doctor. However, infertility also increases the risk of ovarian cancer, even without use of fertility drugs. More research to clarify these relationships is now underway.
Family History of Ovarian Cancer: Ovarian cancer risk is increased among women whose mother, sister, or daughter have, or have had, ovarian cancer, especially if they developed ovarian cancer at a young age. A woman can inherit an increased risk for ovarian cancer from relatives on her mother's side or father's side of the family. About 10% of ovarian cancers result from an inherited tendency to develop the disease. Many cases of familial epithelial ovarian cancer are due to inherited gene mutations that can be identified by genetic testing. Women with ovarian cancers because of inherited gene mutations tend to have a better prognosis than patients who do not have any family history of ovarian cancer. Refer to the section on causes of ovarian cancer for information on these gene mutations. Genetic counseling, genetic testing, and strategies for preventing familial ovarian cancer are discussed in the prevention section of this document.
Breast Cancer: Women who have had breast cancer also have an increased risk of developing ovarian cancer. There are several reasons for this . Some of the reproductive risk factors for ovarian cancer may also increase breast cancer risk. Also, inherited mutations of the BRCA1 and BRCA2 genes greatly increase a woman's risk for both cancers.
Talcum Powder: It has been suggested that talcum powder applied directly to the genital area or on sanitary napkins may be carcinogenic (cancer-causing) to the ovaries. Most, but not all studies suggest a slight increase in risk of ovarian cancer in women who used talc on the genital area. In the past, talcum powder was sometimes contaminated with asbestos, a known cancer-causing mineral. This may explain the association with ovarian cancer in some studies. Body and face powder products have been required by law for over 20 years to be asbestos-free. However, proof of the safety of these newer products will require follow-up studies of women who have used them over a period of many years. There is no evidence at present linking cornstarch powders with any female cancers.
Estrogen Replacement Therapy: Most studies suggest women using estrogens after menopause may have a slightly increased risk of developing ovarian cancer, but some studies have not found any effect on ovarian cancer risk.
A recent study suggested that using estrogen replacement therapy (ERT) increases the risk of developing ovarian cancer, and that the risk increases with continued use. The risk among women who used ERT for longer than 10 years was almost double that of women who had never used it, and the risk among those who used it for 20 years or more was tripled. (Remember, however, that the average lifetime risk for ovarian cancer is only about 2%.) Women who used ERT for less than 10 years or stopped its use more than 15 years ago appeared to have a smaller, but still noticeable, increase in their ovarian cancer risk.
Combined hormone replacement therapy (HRT) refers to use of estrogen and progesterone. Because ERT has been shown to increase endometrial (lining of the uterus) cancer risk but HRT does not, ERT is rarely used any more except in women who have had a hysterectomy (surgical removal of the uterus). The impact of HRT on ovarian cancer risk is not completely known, but studies thus far indicate that there is little, if any, increase.
Cancer is not the only disease influenced by ERT and HRT. These treatments reduce the risk of osteoporosis (weak bones) and bone fractures. Some studies had suggested that ERT and HRT may reduce a woman's risk of heart attacks, but larger, more recent studies have not found this to be the case. At least with regard to HRT, the risk may actually increase slightly with use.
The decision to use HRT or ERT after menopause should be made by a woman and her doctor after weighing the possible risks and benefits. Factors to consider include your other risk factors for ovarian cancer, breast cancer, osteoporosis (thinning and weakening of bones), and the severity of menopausal symptoms.
Support & Information
Ovarian Cancer National Alliance
National Ovarian Cancer Coalition
Cancer BACUP: Understanding Cancer of the Ovary
National Ovarian Cancer Network
The Lynn Cohen Foundation for Ovarian Cancer Research
National Ovarian Cancer Association of Canada
Ovarian Awareness of Kentucky
SHARE (Self-help for Women with Breast Cancer or Ovarian Cancer)