Ovarian cancer occurs when genetic mutations in cells cause tumors to form on or in the ovaries. Tumors of the fallopian tubes and the peritoneum (the lining of the inside of the abdomen) are often grouped together with ovarian cancer because they have similar causes, symptoms, and treatment plans.
Ovarian cancer is caused by genetic mutations that allow cells to divide and grow in a disorganized way. There are two main types of mutations, inherited and acquired.
Inherited mutations that run in families play a role in 20 percent to 25 percent of ovarian cancer cases, but most cancer is caused by acquired mutations. The cause of ovarian cancer is usually unknown.
Normal cells divide in a regular, ordered fashion, forming new cells that are exact copies to replace old ones. Certain genes in each cell are responsible for telling cells when to divide and when to stop dividing. Other genes identify and fix problems in DNA that are copied incorrectly, or cause cells with bad DNA to self-destruct rather than keep multiplying. If a genetic mutation causes one or more of these genes to turn off in some cells, the cells can divide at a faster rate without regulation or order, becoming more and more mutated. Mutations may accumulate, further speeding the unchecked growth of abnormal cells. When these disordered cells begin to invade nearby tissues or break off and migrate to other locations, they have become cancerous.
It is important to note that while science is good at finding correlations — or apparent relationships — between factors and disease, correlation does not prove the factor causes the disease. Many risk factors for ovarian cancer have been identified and are being studied for their role in the development of the disease.
Since genetic mutations cause ovarian cancer, risk factors for ovarian cancer include anything that can encourage mutations. Any woman in the general population of the U.S. has about a 1.2 percent chance of developing ovarian cancer in her lifetime. Inherited mutations from her parents and acquired mutations from age or environmental or lifestyle factors may raise or lower that risk.
Between 20 percent and 25 percent of ovarian cancers are thought to be influenced by genes inherited from parents. If you have a family history of ovarian cancer, your own risk is increased. When a particular gene mutation that is strongly linked to cancer is passed down within a family, it is called a family cancer syndrome.
Hereditary breast and ovarian cancer (HBOC) is a family cancer syndrome that can lead to ovarian or breast cancer, as well as other cancers such as pancreatic cancer. Women with HBOC tend to develop cancer at a younger age or get cancer multiple times. When ovarian cancer runs in families, 65 percent to 85 percent of the time it is caused by mutations in the BRCA1 and BRCA2 genes.
The BRCA genes are needed by cells to repair damage. They are known as “tumor suppressor” genes, and they help prevent cells from turning cancerous. In people with an inherited mutation in one of the BRCA genes, damage can pile up in the cell, leading to additional acquired mutations that cause cancer. BRCA1 and BRCA2 gene mutations raise the risk for developing cancer, but not every woman with these mutations will get cancer. People with a BRCA1 mutation have a 40 percent to 60 percent chance of developing ovarian cancer, and those with a BRCA2 mutation have a 20 percent to 35 percent chance.
Other family cancer syndromes associated with ovarian cancer are caused by different gene mutations. For example, Lynch syndrome is caused by mutations in the repair genes MLH1, MSH2, and MSH6. Lynch syndrome increases a person’s chance of colon, ovarian, stomach, pancreas, kidney, and brain cancers. Cancer may also run in a family, but no known gene mutation can be found. If ovarian cancer runs in your family, genetic testing may help you learn whether you are at increased risk.
Researchers have identified a wide array of environmental factors linked to the development of ovarian cancer. We are all exposed to risk factors throughout our lives. Some are avoidable, while others are outside our control. Anything that raises the risk for acquired gene mutations also raises the risk for developing ovarian cancer.
Mutations in DNA are inevitable. The older you get, the more acquired mutations you will accumulate. However, cancer only develops in a small percentage of people.
A woman’s risk for developing ovarian cancer increases with age. While a few types of ovarian cancer are found in younger women, most cases of ovarian cancer occur in middle-aged or older women. Half of ovarian cancer diagnoses happen in women who are at least 63 years old.
There is a link between ovulation, or the release of an egg from an ovary, and ovarian cancer risk. Experts think this may be because the more a woman is exposed to estrogen, a reproductive hormone that predominates in women, the more likely she is to get cancer. Going through more cycles of ovulation raises risk, and things that block ovulation cause risk to decrease.
Factors that increase a woman’s number of ovulations or estrogen levels, and increase ovarian cancer risk, include:
On the other hand, if a woman has had fewer ovulations, her chance of developing ovarian cancer goes down. Hormone-related factors that decrease a person’s risk of ovarian cancer are:
Some surgeries can also have an effect. Getting tubal ligation, or having the “tubes tied,” can lower a person’s risk for ovarian cancer by 67 percent. Having a hysterectomy can lower risk by 33 percent.
High doses of radiation exposure may increase a person’s risk for cancer. However, this does not appear to be true for ovarian cancer and low doses of radiation. In one study, women who had previously received radiation treatments for other types of cancer were less likely to get ovarian cancer.
Some types of chemicals can increase the risk of various cancers. This hasn’t been well studied in ovarian cancer, but some data shows that chemicals such as pesticides, herbicides, or talcum powder may lead to higher risk. However, other studies have not shown a strong link between talcum powder and ovarian cancer risk. More research is needed to fully understand whether an association exists and to what degree.
Some research has shown that eating high amounts of animal fats increases a person’s risk of ovarian cancer. Animal fats are found in red meat and dairy products, such as milk, butter, and cheese.
Being overweight is linked to several types of cancer. Experts don’t yet know for sure how ovarian cancer risk is affected, but some data shows that women who are obese may be more likely to develop some types of lower-grade ovarian tumors — tumors in which cancer cells appear more like normal cells under a microscope.
Some women use in vitro fertilization (IVF) to help them get pregnant. While some research has found that IVF increases the risk of lower-grade ovarian tumors, other studies have not found a strong link. If you are considering going through IVF or have used it in the past, your doctor can help you understand whether fertility drugs could increase your risk of ovarian cancer.
Sometimes, having had another health condition or another type of cancer makes your risk of ovarian cancer higher. People who have had breast, uterine, rectal, or colon cancer may have an increased chance of getting ovarian cancer. Additionally, having endometriosis raises your risk of getting endometrial or clear cell ovarian cancer.
Ethnicity can influence ovarian cancer predisposition. White women in North America and Europe are most likely to get ovarian cancer. Women of other races have a lower chance of getting ovarian cancer, probably due to a mixture of inherited and environmental factors.
Ashkenazi Jews of Eastern or Central European descent are more likely to have BRCA mutations. Their increased ovarian cancer risk is probably mostly due to inherited mutations.
Black women are less likely to get ovarian cancer. This may be because they are more likely to have more pregnancies and more likely to get a hysterectomy, both of which lower risk. However, the risk for Black women remains lower even after adjusting for these factors.
Women who live in Asian countries are thought to be less likely to get ovarian cancer because of environmental factors, such as diet and lifestyle. When Asian women move to Western countries, their rates of ovarian cancer increase.
Unfortunately, there is no guaranteed way to make sure you don’t get cancer. Some women have a lot of risk factors and don’t get the disease, while the majority of women who are diagnosed don’t have any risk factors. Additionally, most risk factors like age and genetic predisposition are beyond anyone’s control. If you are concerned that you may have a higher risk for developing ovarian cancer, focus on lowering your risk by changing the environmental factors within your control.
If you think you may be at an increased risk, keep an eye out for some of the symptoms of ovarian cancer, such as bloating, abdominal pain, or frequent urination. Talk to your doctor to learn more about how your own individual characteristics may affect your chance of developing cancer.
Ovarian Cancer Condition Guide