Causes & Risks
Ovarian cancer is cancer that forms in the ovaries. Cancer develops when cells mutate and start growing abnormally. Eventually, these cells begin to multiply at a rapid rate and form a tumor. If not caught early, the cancer can spread outside the ovaries to the rest of the reproductive organs and beyond.
It’s not clear exactly what causes ovarian cancer. But, there are certain factors that make you more or less likely to develop the disease. It’s important to keep in mind that having one of these risk factors doesn’t mean you’ll get ovarian cancer. On the other hand, some women get ovarian cancer even though they have no known risk factors.
According to the American Cancer Society (ACS), a woman’s lifetime risk of ovarian cancer is under 2 percent.
Discover the link between ovarian cancer and age »
Types of Ovarian Cancer
There are several types of ovarian cancer. According to the Mayo Clinic, 90 percent of ovarian cancers are epithelial tumors. These tumors begin in a layer of tissue outside the ovaries. Stromal tumors form in hormone-producing cells of the ovaries.
About 7 percent of ovarian cancers are stromal tumors, which are generally diagnosed in the early stages. Germ cell tumors get their start in cells that produce eggs. This rare type of ovarian cancer is usually diagnosed in younger women.
What’s in Your Genes?
Your chance of developing ovarian cancer from epithelial tumors is higher if you have a family history of ovarian, breast, or colorectal cancer. The risk is greater if you have a mother, sister, or daughter who has had ovarian cancer, but your risk can also be tied to your father’s side of the family. This is because about 5 to 10 percent of ovarian cancers come from inherited genetic mutations, according to the ACS.
Mutations of BRCA1 and BRCA2 genes are linked to ovarian cancer, as well as breast cancer, primary peritoneal cancer, and fallopian tube cancer. BRCA gene mutations also increase risk of pancreatic and prostate cancer. With a BRCA1 mutation, the lifetime risk of ovarian cancer is between 35 and 70 percent. With a BRCA2 mutation, the lifetime risk is between 10 and 30 percent by age 70.
Some other genes that may increase the likelihood of ovarian cancer include PTEN, STK11, and MUTYH. You can’t do anything about your genes, but if you have a family history of ovarian cancer, discuss the pros and cons of genetic testing with your doctor.
Why Personal Medical History Matters
Medical history also plays a role in risk. For example, you’re at an increased risk of ovarian cancer if you’ve already had breast cancer. That risk is even higher if you also have a family history of breast cancer.
Other conditions that may increase risk of ovarian cancer include
endometriosis, a disease in which cells that line the uterus grow somewhere else
polycystic ovary syndrome, an endocrine system disorder
PTEN tumor hamartoma syndrome, a group of disorders resulting from genetic mutation
hereditary nonpolyposis colon cancer, caused by many of the same genes that increase risk for ovarian cancer
Peutz-Jeghers syndrome, caused by mutations in the STK11 gene
MUTYH-associated polyposis, caused by mutations in the MUTYH gene
Tell your doctor if you’ve previously been diagnosed with any of these conditions.
How Birth Control and Reproductive History Matter
Using oral contraception may actually lower your risk of ovarian cancer. Your risk can be lowered after only a few months on the pill. According to the National Cancer Institute (NCI), this protection may last as long as 30 years.
Fertility drugs, however, may increase the risk of ovarian tumors with “low malignant potential.” These tumors are made up of abnormal cells that can potentially become cancerous. The chance of this happening, however, is rare.
If you’ve had your tubes tied, the risk of ovarian cancer is lowered by about two-thirds. Removal of the uterus through a hysterectomy reduces the risk by about one-third.
You’re also at an increased risk if you started having periods before age 12, or if you didn’t go through menopause until after age 52. Menopausal women who take hormone replacement therapy, particularly estrogen alone, may be at higher risk of ovarian cancer.
The risk of ovarian cancer is lower if you’ve carried a baby to term before age 26. Each pregnancy decreases the risk. Having your first pregnancy after your 35th birthday, or never carrying a pregnancy to term, puts you at a higher risk.
Breastfeeding may also lower the risk of ovarian cancer.
Age and Ethnicity Have Something to Do with It
As is the case for many types of cancer, risk increases with age. You’re more likely to develop ovarian cancer after menopause. It’s quite rare in women under age 40. According to ACS, half of all diagnoses occur in women age 63 or older.
White women in Europe and North America have the highest rates of ovarian cancer. The lowest rates occur in black women. Asian women also have a lower rate, but it rises if they relocate to Western countries.
Diet and Body Size Play a Role
The relationship between ovarian cancer and diet is unclear. However, a body
mass index (BMI) of 30 or higher increases risk. Adolescent obesity or gaining more than 40 pounds during adulthood is linked to higher risk of death from ovarian cancer, according to the NCI. Women who are 5 feet 8 inches or taller are also at a slightly higher risk.
Controlling Risk
Some risk factors for ovarian cancer, including your genes and your age, are beyond your control. But you can change others. In general, a healthy diet rich in plant-based foods, regular physical activity, and a healthy body weight can lower your risk of cancer.
