Ovarian Cancer - Risk Factors

The following have been identified as factors that increase a woman’s risk of developing ovarian cancer. While women with one or more of these risk factors have a higher-than-average chance of developing ovarian cancer, the majority of these women will never develop the disease. Conversely, many women who develop ovarian cancer have no known risk factors for the disease. It is important that women know the risk factors and symptoms of ovarian cancer to help increase the chance that it will be detected early.

• Risk Factors that Cannot Be Controlled
• Risk Factors that Can Be Controlled

Risk factors that cannot be controlled:

Age: The risk of ovarian cancer increases with age. The majority of ovarian cancer diagnoses occur in women who have already reached menopause. According to the National Cancer Institute, the highest incidence of ovarian cancer occurs in women over age 60. However, ovarian cancer can also affect younger women.

Family history of ovarian cancer: Women who have a family history of ovarian cancer are at higher risk of developing the disease than those with no family history. The risk is higher if a woman’s close relatives (mother or sisters) have been diagnosed with ovarian cancer (the risk is 5% over a lifetime compared with a 1.5% risk if no relatives have been diagnosed with ovarian cancer).

Genetics: BRCA1 (breast cancer gene 1) and BRCA2 (breast cancer gene 2) are two genes that, when functioning normally, help repair damage to DNA (a process that also prevents cancer development). However, women who carry mutations of BRCA1 or BRCA2 are at higher risk of developing both ovarian and breast cancer compared to women who do not have these genetic mutations.

Approximately 9% of ovarian cancer cases are due to a genetic mutation of BRCA1 or BRCA2. The American Cancer Society estimates that between 56% and 87% of women with inherited BRCA1 or BRCA2 mutations will develop breast cancer by age 70. The lifetime ovarian cancer risk for women with BRCA1 or BRCA2 mutations is estimated to be between 17% and 44%. Women with a strong family history of ovarian or breast cancer may wish to talk to their physicians about undergoing genetic testing to determine whether they carry the BRCA gene mutations. Click here to learn more about genetic testing.

Hereditary nonpolyposis colon cancer (HNPCC): Women with HNPCC are also at slightly higher risk of developing ovarian cancer. HNPCC is a condition caused by inherited genes and usually develops in younger women (under 40) with a strong family history of HNPCC. In addition to an increased risk of ovarian cancer, HNPCC puts women at very high risk of colon cancer and endometrial cancer (cancer of the uterine lining).

Early menstruation/late menopause: Women who begin menstruating before age 12 or those who do not reach menopause until after age 50 are at an increased risk for ovarian cancer as well as breast cancer. This may be because women who have more menstrual cycles throughout their lifetime are at higher risk of ovarian and breast cancer. Research suggests that women who become pregnant, breast-feed, or take birth control pills are at a lower risk of developing ovarian cancer.

Personal/family history of breast cancer: Women who have been diagnosed with breast cancer have an increased risk of developing ovarian cancer because many of the risk factors for breast cancer (including early menstruation, late menopause, delayed childbirth, BRCA gene mutations, etc.) also put women at risk for ovarian cancer.

Risk factors that can be controlled:

Delayed childbirth: Having a first child after age 30 or never having children increases the risk for ovarian cancer and breast cancer. Pregnancy seems to decrease the risk of ovarian and breast cancer if a woman becomes pregnant with her first child before age 30. This is because there is an interruption of menstrual cycles during pregnancy. Women who never become pregnant are at a higher risk of ovarian and breast cancer than those who have a first child before age 30. However, pregnancy after age 30 appears to also increase the risk of ovarian and breast cancer. The older a woman is, the more likely her ovarian and breast tissue has already been exposed to some cancer-causing substances called carcinogens. Therefore, exposure to elevated hormone levels during pregnancy at a later age may stimulate the growth of abnormal ovarian or breast tissue. In fact, some experts believe that the number of menstrual cycles that occur between a woman’s first menstrual period and her first pregnancy is a greater predictor of ovarian cancer and breast cancer risk than her age at her first menstruation or menopause.

Use of fertility drugs: Some research has suggested that women who use (or have used) fertility drugs are at higher risk of developing ovarian cancer. In particular, the fertility drug clomiphene citrate may increase the risk of ovarian cancer. The risk may be greater if the woman does not become pregnant from using fertility pills. Women who are considering fertility drugs should talk to their physicians about the benefits and risks.

Use of talc/talcum powder: Some research has suggested that the use of talc or talcum powder, when applied to sanitary napkins, diaphragms, condoms, or directly to the genitals, increases a woman’s risk for ovarian cancer. According to the American Cancer Society, many talcum powders in the past were contaminated with asbestos, which may explain the increase in ovarian cancer risk. However, until further research is conducted, women should avoid using talcum powder on the genital area. Cornstarch powders, which have not been linked to ovarian cancer, can be substituted instead.

Use of estrogen replacement therapy: Studies have shown that the long-term use of estrogen replacement therapy (ERT, estrogen without progesterone) may slightly increase the risk of ovarian cancer. In a 2001 study of more than 200,000 women who took ERT for over 10 years, 944 deaths from ovarian cancer were recorded over a 14-year follow-up period. The researchers found that using ERT for 10 or more years doubled the risk of developing ovarian cancer (from 1% to 2%). Further research is needed to determine whether combination hormone replacement therapy (estrogen and progesterone) poses this same risk. Because hormone replacement therapy can provide many benefits (such as relief from menopausal symptoms, prevention of osteoporosis, and possible protection from heart disease), women should discuss the benefits and risks of taking hormone replacement therapy with their physician, based on their individual medical circumstances. Click here to learn more about hormone replacement therapy.

Updated: January 10, 2008