Research has shown that certain risk factors increase the likelihood a woman may get ovarian cancer. Other factors may actually decrease a woman’s probability of getting the disease. Having risk factors does not predict you will get ovarian cancer. Some women who get the disease have no known risk factors, and most women with the risk factors will not get ovarian cancer. However, if you think you may be at risk for ovarian cancer, you should speak with your doctor. You can also view an ovarian cancer risk questionnaire.
Factors that may increase the risk of ovarian cancer:
Genetics: BRCA1 and BRCA2
About 20 to 25 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 10 to 15 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. You can find more detail about BRCA1 and BRCA2 mutations in the Ovarian Cancer Risk Consensus Statement—BRCA1 and BRCA2, which the Alliance endorsed in 2012.
Genetics: Lynch Syndrome
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 colorectal cancer, women with HNPCC have about a 12 percent lifetime risk of developing ovarian and a 40-60 percent chance of developing uterine cancer.
Women with a grandmother, mother, daughter or sister 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).
While it accounts for only a limited number of cases, heredity is a strong risk factor for ovarian cancer. Family history should be considered; however, many women without a family history may still have a gene mutation associated with risk for ovarian cancer. All women diagnosed with ovarian cancer, primary peritoneal or fallopian tube cancer should be referred for genetic counseling and consideration of genetic testing.
Family history of any of the following cancers may indicate an increased risk: Breast cancer, Ovarian cancer, Colon cancer, Uterine cancer, Rectal cancer.
Personal history of cancer or endometriosis
Women who have had cancer of the breast, uterus, colon or rectum have a higher risk of ovarian cancer. Having endometriosis increases the risk of clear cell and endometrioid ovarian cancers 2-3 fold.
All women are at risk of developing ovarian cancer regardless of age; however ovarian cancer rates are highest in women aged 55-64 years. The median age at which women are diagnosed is 63, meaning that half of women are younger than 63 when diagnosed with ovarian cancer and half are older.
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.
Reducing Ovarian Cancer Risk
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 health care professional can help a woman identify ways to reduce her risk as well as decide if consultation with a genetic counselor is appropriate.
Oral Contraceptive Use
The use of oral contraceptives (birth control pills) 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.
Pregnancy and Breastfeeding
Pregnancy and breastfeeding are linked with a reduced risk of ovarian cancer, likely because women ovulate less frequently when pregnant or breastfeeding. Multiple pregnancies or having first full-term pregnancy before the age of 26 decreases risk.
Removal of the Ovaries and Fallopian Tubes
Women can greatly reduce their risk of ovarian cancer by removing their ovaries and fallopian tubes, a procedure known as prophylactic bilateral salpingo oophorectomy. Primary peritoneal cancer, which is microscopically almost identical to ovarian cancer, can still occur, but is infrequent. One recent study suggests that women with BRCA1 mutations gain the most benefit by removing their ovaries before age 35.
There are risks associated with removing the ovaries and fallopian tubes; women should speak to their doctors about whether this procedure is appropriate for them.
Having a hysterectomy, or removal of the uterus while leaving the ovaries, may decrease the risk of ovarian cancer by 33 percent, according to the American Cancer Society. Having fallopian tubes tied (tubal ligation) may reduce risk by up to 67 percent, the American Cancer Society says, though researchers aren’t sure why this is the case.