While most women with ovarian cancer do not have any known risk factors, some do exist. If a woman has one or more risk factors, she will not necessarily develop ovarian cancer; however, her risk may be higher than the average woman’s.
About 10 to 15 percent of women diagnosed with ovarian cancer have a hereditary tendency to develop the disease. The most significant risk factor for ovarian cancer is an inherited genetic mutation in one of two genes: breast cancer gene 1 (BRCA1) or breast cancer gene 2 (BRCA2). These genes are responsible for about 5 to 10 percent of all ovarian cancers.
Eastern European women and women of Ashkenazi Jewish descent are at a higher risk of carrying BRCA1 and BRCA2 mutations.
Since these genes are linked to both breast and ovarian cancer, women who have had breast cancer have an increased risk of ovarian cancer.
Another known genetic link to ovarian cancer is an inherited syndrome called hereditary nonpolyposis colorectal cancer (HNPCC or Lynch Syndrome). While HNPCC poses the greatest risk of colon cancer, women with HNPCC have about a 12 percent lifetime risk of developing ovarian cancer.
Women who have one first-degree relative with ovarian cancer but no known genetic mutation still have an increased risk of developing ovarian cancer. The lifetime risk of a woman who has a first degree relative with ovarian cancer is five percent (the average woman’s lifetime risk is 1.4 percent).
All women are at risk of developing ovarian cancer regardless of age; however, a woman’s risk is highest during her 60s and increases with age through her late 70s.
About 69 percent of women diagnosed with ovarian cancer in the United States from 2002 to 2006 were 55 or older.
The median age (at which half of all reported cases are older and half are younger) at diagnosis is 63.
Reproductive History and Infertility
Research suggests a relationship between the number of menstrual cycles in a woman’s lifetime and her risk of developing ovarian cancer. A woman is at an increased risk if she:
- started menstruating at an early age (before 12),
- has not given birth to any children,
- had her first child after 30,
- experienced menopause after 50,
- has never taken oral contraceptives.
Infertility, regardless of whether or not a woman uses fertility drugs, also increases the risk of ovarian cancer.
Hormone Replacement Therapy
Doctors may prescribe hormone replacement therapy to alleviate symptoms associated with menopause (hot flashes, night sweats, sleeplessness, vaginal dryness) that occur as the body adjusts to decreased levels of estrogen. Hormone replacement therapy usually involves treatment with either estrogen alone (for women who have had a hysterectomy) or a combination of estrogen with progesterone or progestin (for women who have not had a hysterectomy).
Women who use menopausal hormone therapy are at an increased risk for ovarian cancer. Recent studies indicate that using a combination of estrogen and progestin for five or more years significantly increases the risk of ovarian cancer in women who have not had a hysterectomy. Ten or more years of estrogen use increases the risk of ovarian cancer in women who have had a hysterectomy.
Various studies have found a link between obesity and ovarian cancer. A 2009 study found that obesity was associated with an almost 80 percent higher risk of ovarian cancer in women 50 to 71 who had not taken hormones after menopause.
Women can reduce the risk of developing ovarian cancer in many ways; however, there is no prevention method for the disease. All women are at risk because ovarian cancer does not strike only one ethnic or age group. A healthcare professional can help a woman identify ways to reduce her risk as well as decide if consultation with a genetic counselor is appropriate.
Oral Contraceptives (birth control pills)
The use of oral contraceptives decreases the risk of developing ovarian cancer, especially when used for several years. Women who use oral contraceptives for five or more years have about a 50 percent lower risk of developing ovarian cancer than women who have never used oral contraceptives.