Causes, Risk Factors, and Prevention of Ovarian Cancer

Ovarian cancer doesn’t have a single known cause, but several factors can raise or lower your risk. If you have a family history of ovarian cancer or an inherited gene mutation such as BRCA1 or BRCA2, there are some ways to lower your risk or help prevent certain types of ovarian cancer.

What causes ovarian cancer?

The exact cause of most ovarian cancers is not known, but researchers have found several factors that can affect the risk of epithelial ovarian cancer. These include:

• Older age
• Inherited gene mutations, such as BRCA1, BRCA2, or Lynch syndrome
• Starting menstrual cycle before 12 years old
• Starting menopause after 52 years old
• No personal history of giving birth
• Endometriosis (abnormal growth of tissue that lines the inside of the uterus)
• Radiation exposure to the pelvis

Much less is known about risk factors for germ cell and stromal tumors of the ovaries.

Gene changes related to ovarian cancer

Researchers have made great progress in understanding how certain gene mutations (changes) can cause normal cells to become cancerous. For example, some genes contain instructions for controlling when our cells grow and divide. Mutations in these genes can lead to the development of cancer.

Scientists are also learning more about how these genes work when they’re healthy—and how disrupting their function can lead to cancer. This research is expected to lead to new drugs for preventing and treating familial ovarian cancer in the future.

Inherited genetic mutations

A small portion of ovarian cancers occur in women with inherited mutations that increase cancer risk. These mutations can be passed down through families and some are linked to certain cancer syndromes.

Mutations linked to a higher risk of ovarian cancer include:

• BRCA1, BRCA2, and other homologous recombination genes
• PTEN (linked to PTEN tumor hamartoma syndrome)
• STK11 (linked to Peutz-Jeghers syndrome)
• MUTYH (linked to MUTYH-associated polyposis)
• MLH1, MLH3, MSH2, MSH6, TGFBR2, PMS1, PMS2 and others (linked to hereditary nonpolyposis colorectal cancer or Lynch syndrome)

Genetic testing can detect these inherited mutations. If you have a family history of cancers linked to these syndromes, such as breast and ovarian cancer, thyroid and ovarian cancer, or colorectal and endometrial (uterine) cancer, ask your doctor about genetic counseling and testing.

The American Cancer Society recommends discussing genetic testing with a qualified cancer genetics professional before any genetic testing is done. For more, see Genetics and Cancer.

Research in this area has already led to better ways to detect high-risk genes and estimate a person’s ovarian cancer risk. A better understanding of how genetic and hormonal factors (such as oral contraceptive use) interact may also lead to new ways to prevent ovarian cancer.

Acquired genetic mutations

Most gene mutations related to ovarian cancer are not inherited. Instead, they occur during a person’s life and are called acquired mutations. In some cancers, these mutations may be caused by radiation or harmful chemicals, but there is no evidence for this in ovarian cancer. So far, no specific chemical in the environment or in our diets has been clearly linked to mutations that cause ovarian cancer. In most cases, the cause of these acquired mutations is still unknown.

Most ovarian cancers have several acquired mutations. Tests can identify some of these, such as changes in the TP53 tumor suppressor gene or the HER2 oncogene. More research is needed to understand whether this information could help predict a person’s prognosis.

Why ovarian cancer might develop

It usually takes several gene mutations over time for normal cells to become cancer. Researchers are still studying why these changes happen. Here are some reasons why this might happen in ovarian cancer:

• Damage to the ovaries: Every time a person ovulates (releases an egg), it can cause damage to the ovary. Over time, this may lead to cancer.
• Inflammation and aging: As people get older, our bodies can become more inflammatory, even without an infection. This may raise the risk of cancer.

Can ovarian cancer be prevented?

Most women have one or more risk factors for ovarian cancer, but most of these only slightly increase risk. They don’t fully explain why ovarian cancer is relatively common. So far, knowing about these risk factors hasn’t led to practical ways to prevent ovarian cancer.

If you are concerned about your risk of ovarian cancer, talk to your health care team. They can help you understand your risk and explore possible ways to lower it.

Ways to lower your risk of ovarian cancer

There are several ways to reduce your risk of developing the most common type of ovarian cancer, epithelial ovarian cancer, including certain procedures and lifestyle choices such as:

• Surgery to remove certain reproductive organs (such as oophorectomy)
• Using an IUD (intrauterine device)
• Taking birth control medication
• Having children
• Breastfeeding

Much less is known about ways to lower the risk of developing germ cell and stromal tumors of the ovaries, so this information does not apply to those types.

Learn more: Ovarian Cancer Risk Factors

If you have a family history of ovarian cancer

If your family history suggests that you or a close relative might have a syndrome linked with a high risk of ovarian cancer, consider genetic counseling and testing. Genetic counseling involves reviewing your personal medical and family history and is done by a genetic counselor or other health care professional. This can help predict whether you are likely to have one of the gene mutations associated with an increased ovarian cancer risk.

The counselor will also discuss the benefits and potential drawbacks of genetic testing with you. Genetic testing can help determine if you or members of your family carry certain gene mutations that cause a high risk of ovarian cancer. However, the results are not always clear, and a genetic counselor can help you sort out what the results mean to you.

If you have a gene mutation associated with ovarian cancer

Knowing that you have a mutation such as BRCA1 or BRCA2 can be very helpful in making important decisions about certain prevention strategies for yourself and your children.

These prevention strategies include:

• Surgery: Usually, surgery is recommended to remove both ovaries and fallopian tubes. This is called risk-reducing or prophylactic salpingo-oophorectomy. In certain cases, removing only the fallopian tubes (salpingectomy) or removing only the uterus (hysterectomy) may be an option.
• Medications: Your doctor may recommend medications, such as oral contraception pills, to lower your risk of cancer.
• Screening: Close screening with imaging and with blood work, such as tumor marker tests, may be recommended.

If you are considering surgery, mathematical models can help estimate how many years of life an average person with a BRCA mutation might gain by having both ovaries and fallopian tubes removed before cancer starts. Although these tools can predict average outcomes for large groups, they cannot predict what will happen for any one person.

Removing the ovaries can also lower the risk of breast cancer for premenopausal women with BRCA gene mutations. The risk of ovarian cancer is reduced by 85% to 95%, and the risk of breast cancer cut by 50% or more.

What’s new in ovarian cancer prevention?

Many experts now believe that some ovarian cancers (especially high-grade serous carcinomas) and many primary peritoneal cancers actually start in the fallopian tubes. According to this theory, early cancer cells can form in the fallopian tubes, break away, and attach to the surface of the ovaries or peritoneum. Once in these new places, the cancer cells may grow more quickly.

This idea could affect surgical options for preventing ovarian cancer. Some people at high risk may have the option to remove only their fallopian tubes at first. The ovaries could then be removed later. This approach may help avoid or delay problems caused by the loss of estrogen from the ovaries, such as bone loss, heart disease, and menopause symptoms.

Researchers are studying whether this 2-step approach is an effective way to prevent ovarian cancer. However, it’s not likely to lower breast cancer risk as much removing the ovaries earlier.