Causes
About 22,220 new cases of ovarian cancer are expected in the United States in 2005. Evidence suggests that the incidence of ovarian cancer is declining. The average age for the onset of ovarian cancer is about 60, although ovarian cancer can develop in women from the age of 20 to 90. The lifetime risk of ovarian cancer in women with no family history of the disease is approximately one in 70 (1.4%).
Women with a history of ovarian cancer in one first-degree relative (mother or sister) have an overall risk of 5% of developing the disease, but it may be higher in women with specific genetic factors. The majority of women with ovarian cancer have no family history of the disease, however, meaning that genetic inheritance is not the only risk factor.
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Genetic mutations causing abnormal cell growth and differentiation are the basis for all cancer. The great majority of genetic defects that cause cancer are due to unknown causes. Most likely overexposure to environmental assaults or errors that occur during cell division play a role in many cases.
The Role of Hormones and Ovarian Stimulation
A number of circumstances that create hormonal changes may increase the risk of ovarian cancer.
Number of Ovulations. Risk of ovarian cancer is directly related to the number of times a woman ovulates, which is indicated by the total number of menstrual periods she has had. A lower number of ovulations occur when the menstrual periods are shut off (as in pregnancy), so the risk of developing ovarian cancer is reduced.
The following women have a lower risk for ovarian cancer:
- Women with a history of multiple pregnancies.
- Women who took birth control pills (which shuts off the menstrual period).
- Women who breast-fed. (The body usually does not release eggs while a woman is breast-feeding.)
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