Risk factors for ovarian cancer

Certain behaviours, substances or conditions can affect your risk, or chance, of developing cancer. Some things increase your risk and some things decrease it. Most cancers are the result of many risks. But sometimes cancer develops in people who don't have any risks.

Epithelial ovarian carcinoma is the most common type of ovarian cancer. The number of new cases of this cancer (called the incidence) increases with age. Most epithelial ovarian carcinomas are found in women who have gone through menopause.

Some people with certain genetic conditions have a higher than average risk for ovarian cancer. Talk to your doctor about your risk. If you have a genetic condition that increases the risk of ovarian cancer, you may need to visit your doctor more often to check for ovarian cancer. Your doctor will recommend what tests you should have and how often you should have them.

The following can increase or decrease your risk for epithelial ovarian carcinoma. The risks for less common types of ovarian cancer are not well known and may not be the same as for epithelial ovarian carcinoma. But epithelial ovarian carcinoma and fallopian tube cancer share many of the same risk factors. Some experts think that this may be because some epithelial ovarian carcinomas can begin in a fallopian tube.

Family history of ovarian cancer

BRCA gene mutations

Lynch syndrome

Family history of certain cancers

Personal history of breast cancer

Pregnancy

Gynecological surgery

Hormone replacement therapy

Birth control pills

Smoking tobacco

Asbestos

Tall adult height

Excess weight

Endometriosis

Sedentary behavior

A family history of ovarian cancer means that 1 or more close blood relatives have or had ovarian cancer. Sometimes ovarian cancer develops in a family more often than would be expected by chance. It may not be clear if the family’s pattern of cancer is due to chance, shared lifestyle factors, a genetic risk passed from parents to children or a combination of these factors.

If several of your relatives have ovarian cancer, you can have a higher risk of developing the disease. These relatives can be on either your mother’s or your father’s side of the family.

You can have a higher risk of developing ovarian cancer if you have 1 first-degree relative (mother, sister or daughter) with the disease. The risk of developing ovarian cancer is greater if your mother had the disease than if your daughter had it. Your risk can be even higher if your relative was diagnosed with ovarian cancer before they were 50 years of age or before they went into menopause.

Having 2 or more first-degree relatives with ovarian cancer can also increase your risk for the disease.

You can have a slightly higher risk for ovarian cancer if you have 1 first-degree relative and 1 second-degree relative (aunt, grandmother or niece) with the disease.

Breast cancer gene 1 (BRCA1) and breast cancer gene 2 (BRCA2) normally help control the growth of cancer cells. Mutations in these genes (which can be inherited from either parent) increase the risk for breast cancer. These mutations also increase the risk for ovarian cancer. But not all women with mutations in the BRCA1 or BRCA2 gene will develop ovarian cancer.

Overall, the BRCA1 mutation increases the risk for ovarian cancer more than the BRCA2 mutation. Women with the BRCA1 mutation are more likely to develop ovarian cancer before they are 50 years of age. Women with the BRCA2 mutation are more likely to develop the disease after they are 60 years of age. Ovarian cancer is usually diagnosed at a younger age in women who do not have a BRCA gene mutation.

Ovarian cancer is likely linked to an inherited BRCA1 or BRCA2 gene mutation if the woman has:

• several family members with breast or ovarian cancer
• 1 or more female relatives who developed breast cancer before they were 50 years of age
• a relative with both breast and ovarian cancer
• family members who develop cancer in both breasts (called bilateral breast cancer)
• a male relative with breast cancer
• Ashkenazi (Eastern European) Jewish ancestry

Women with ovarian cancer related to a BRCA gene mutation also have a higher than average risk of developing breast and other cancers. Talk to your doctor about your risks. Genetic risk assessment and genetic testing may be an option for some women.

Lynch syndrome is an inherited condition that causes a large number of polyps to develop in the lining of the colon and rectum, but not as many polyps as are found in familial adenomatous polyps (FAP).

There are 2 types of Lynch syndrome. Type A increases the risk for colorectal cancer. Type B increases the risk for several cancers, including colorectal and other digestive system cancers, and ovarian and uterine cancers in women. Because of its connection to colorectal cancer, Lynch syndrome is also called hereditary non-polyposis colorectal cancer (HNPCC).

Women who have a family history of breast cancer have a higher risk of developing ovarian cancer. A family history of colorectal, uterine or pancreatic cancer also increases the risk for ovarian cancer.

Women who have been diagnosed with breast cancer have a higher risk of developing ovarian cancer. This could be because of a BRCA gene mutation. Some of the same risk factors for breast cancer that are related to a woman's menstruation history may also increase her risk of developing ovarian cancer. These risk factors include starting your period early (younger than 11 years of age) or starting menopause later (after age 55).

Women who have never been pregnant have a higher risk of developing ovarian cancer than women who have been pregnant. Researchers think that the lower risk may be because the hormones that are present during pregnancy have a protective effect. It is possible that the higher risk in women who have never been pregnant is linked to the factors that may make it difficult for her to become pregnant.

The risk for ovarian cancer is also higher in women who have never given birth, even if they have been pregnant. Researchers are not sure if this greater risk is related to the same factors that increase the risk for ovarian cancer in women who have never been pregnant.

Having been pregnant lowers the risk of developing ovarian cancer. The more times you've been pregnant, the greater the protective effect. But pregnancy does not appear to have a protective effect for women who have a strong family history of ovarian cancer or a BRCA gene mutation.

A tubal ligation is surgery that cuts or blocks the fallopian tubes. A salpingectomy is surgery to remove the fallopian tubes. Having either of these surgeries lowers a woman's lifetime risk of developing ovarian cancer.

A hysterectomy is surgery to remove the uterus. It may also lower the risk of developing ovarian cancer, but not as well as tubal ligation. Hysterectomy seems to lower the risk when the fallopian tubes and ovaries are also removed (called bilateral salpingo-oophorectomy).

Women with BRCA1 or BRCA2 mutations who have a higher risk for developing ovarian cancer may be offered a bilateral sapling-oophorectomy to reduce their risk of developing ovarian cancer.

Hormone replacement therapy (HRT) uses female sex hormones (estrogen, progesterone or both) to manage the symptoms of menopause, such as hot flashes, vaginal dryness and mood swings. Research suggests that HRT with estrogen alone, as well as combined HRT with both estrogen and progesterone, increase the risk for ovarian cancer. The longer you take estrogen, the greater your risk for the disease. Women who have taken HRT for more than 5 years have a greater risk than women who have taken it for less than 5 years. Current users of HRT have a higher risk compared to women who have stopped taking HRT, no matter how long they took it.

Talk to your doctor about the benefits and risks of taking HRT.

Birth control pills (oral contraceptives) are designed to prevent pregnancy. They contain the hormones estrogen and progesterone. Birth control pills lower your risk for ovarian cancer. Learn more about the benefits and risks of hormonal birth control.

Smoking tobacco increases your risk for mucinous carcinoma (a type of epithelial ovarian carcinoma).

All forms of tobacco, including cigarettes, cigars and pipes, increase your risk. The more you smoke and the longer you smoke, the greater your risk. The risk of developing mucinous carcinoma decreases with time after you quit smoking.

Learn more about how to live smoke-free.

Asbestos is a group of minerals that occur naturally. It has been widely used in building materials and many industries. Asbestos increases the risk for ovarian cancer.

Learn more about asbestos and cancer and how to be safe at work.

Tall women have a slightly higher risk for ovarian cancer. Researchers think this increased risk may be due to developmental factors such as growth and puberty hormones.

Overweight and obesity increase the risk for ovarian cancer. Learn more about how to have a healthy body weight.

The endometrium is the lining of the uterus. Endometriosis occurs when the endometrium grows outside of the uterus. It can grow on the ovaries, behind the uterus, on the small intestine, on the large intestine or on the bladder. Women with endometriosis have a higher risk of developing ovarian cancer, especially if the endometriosis involves the ovaries. Other studies show that the risk for certain types of ovarian cancer, including clear cell and endometrioid tumours, may be higher in women with endometriosis.

Sedentary behaviour, or sitting for long periods of time, increases your risk for ovarian cancer. Learn more about how to move more, sit less.

The following have been linked with ovarian cancer, but there is not enough evidence to know for sure that they are risks. More research is needed.

• number of menstrual periods during your lifetime, including the number of ovulations, starting periods before 12 years of age (early menstruation or menarche) or stopping periods after the age of 55 (late menopause)

• talcum powder
• not eating enough vegetables

The following have been linked with a decreased risk of ovarian cancer, but more research is needed to know for sure that they lower the risk.

• breastfeeding

• aspirin

Significant research shows that there is no link between alcohol or coffee and a higher risk for epithelial ovarian carcinoma.

To make the decisions that are right for you, ask your doctor questions about risks. Learn how cancer can be prevented and what you can do to reduce your risk.