Endometriosis and Ovarian Cancer Risk: What's Known

Endometriosis is linked to a higher risk of ovarian cancer, but that risk is easy to overstate. The rise shows up mainly for a few subtypes. In absolute terms, it stays small. Endometriosis is not cancer. Most people who have it will never get ovarian cancer.

If you live with this condition, this page explains the research. It covers what is known, what is not, and what to ask your care team.

The National Institute of Child Health and Human Development (NICHD) studies this disease. It defines endometriosis as a disease in which tissue similar to the lining of the uterus grows in other places in the body. It is one of the most common gynecological diseases. Its main symptoms are pain and trouble getting pregnant.

The pain takes many forms. NICHD lists strong menstrual cramps that may worsen over time. It lists pain during or after sex, and pain in the intestine or lower abdomen. Painful bowel movements or urination during periods are on the list too. Heavy periods and spotting between periods can occur. So can digestive symptoms that resemble a bowel disorder, and fatigue.

There is no cure yet. But there are effective treatments for the symptoms.

NCI's patient summary on prevention states it plainly. Women who have endometriosis have an increased risk of ovarian cancer. NICHD adds two details. The increase is slight. And it appears especially in women who were diagnosed at an early age.

NCI's evidence review gives numbers. In a large pooled study, the condition was tied to about three times the odds of clear cell ovarian cancer. It was tied to about twice the odds of the endometrioid subtype. Low-grade serous tumors showed about twice the odds as well. A Danish registry study of women with endometriosis found higher rates of clear cell cancer (about 3.6 times the expected rate) and endometrioid cancer (about 1.6 times). It reported no increased risk of serous or mucinous subtypes.

No link was found with mucinous tumors. None was found with high-grade serous tumors either. That matters, because NCI calls high-grade serous the most common and most lethal ovarian carcinoma subtype.

Ratios sound alarming until you attach a baseline. NCI notes that the lifetime risk of ovarian cancer in the population is 1.12 percent. The subtypes tied to endometriosis are less common than that. NCI puts their lifetime risk at about 0.2 percent. With endometriosis, that rises to about 0.4 to 0.6 percent.

Put another way: even with this condition, well over 99 out of 100 women will not develop these subtypes. The link is worth knowing. It is not a prediction.

NICHD is careful on cause and effect. It is unclear whether endometriosis causes ovarian cancer. The two conditions may instead share risk factors. Some studies also found small links to other cancers. NICHD calls those links much less clear.

This link does not come with a routine test to request. What it supports is awareness of your own history, and a good working relationship with your care team.

Endometriosis and ovarian problems can share territory. Pelvic pain, digestive complaints, and pain with sex show up in both. That overlap is one reason people with the condition worry.

A practical habit helps: know your own pattern. NICHD says endometriosis pain often eases after menopause, though hormone therapy for menopause symptoms may keep it going. A symptom that is new, or different from your usual flares, deserves a mention to your care team. So does one that will not let up. Not because it is probably cancer — it usually is not — but because it is a change. Our pages on pelvic pain and bloating cover those symptoms in depth.

NCI's prevention summary lists factors linked with lower risk in studies. Oral contraceptives are one, and NCI says the lower risk can last more than 30 years after stopping. Giving birth and breastfeeding are on the list. So are tubal ligation and salpingectomy, which is removal of the fallopian tubes. For people at high inherited risk, risk-reducing surgery is a separate and bigger topic.

None of these is a blanket recommendation. Each has tradeoffs. Some only come up during other medical decisions. The useful move is simple. Bring your endometriosis history into those talks, so your care team can weigh it with everything else about you.

• Ovarian, Fallopian Tube, and Primary Peritoneal Cancer Prevention (PDQ) — Patient Version — National Cancer Institute
• Ovarian, Fallopian Tube, and Primary Peritoneal Cancer Prevention (PDQ) — Health Professional Version — National Cancer Institute
• Endometriosis — Eunice Kennedy Shriver National Institute of Child Health and Human Development
• Other Endometriosis FAQs — NICHD
• What are the symptoms of endometriosis? — NICHD