Women with severe endometriosis are 10 times more likely to develop ovarian cancer than women who do not have endometriosis, according to research from the Huntsman Cancer Institute at the University of Utah, the Spencer Fox Eccles School of Medicine at the U, and Boston University Chobanian and Avedisian School of Medicine.

 

Prior studies have shown a causal connection between endometriosis and ovarian cancer, but in using the Utah Population Database – a repository of linked health records housed at the Huntsman Cancer Institute – investigators were able to analyse the incidence rates of different types of endometriosis and subtypes of ovarian cancer in more than 78,000 women.

 

“These are really important findings,” said Jennifer Doherty, investigator and co-leader of cancer control and population sciences at the Huntsman Cancer Institute and professor of the population health sciences department at the University of Utah.

 

“This impacts clinical care for individuals with severe endometriosis, since they would benefit from counseling about ovarian cancer risk and prevention. This research will also lead to further studies to understand the mechanisms through which specific types of endometriosis cause different types of ovarian cancer.”

 

The project began as a collaboration between Ms Doherty, Mollie Barnard, assistant professor of medicine at Boston University School of Medicine and Karen Schliep, associate professor of public health at the University of Utah. Schliep served as senior and corresponding author of the study.

 

“Karen was researching endometriosis, and Mollie and I were working on ovarian cancer. We mutually approached each other about putting the data from our two studies together, and that’s how this very powerful combined analysis happened,” says Doherty. “It’s hard to have a large enough study to be able to observe the results we did—all thanks to the Utah Population Database.”

 

Endometriosis is a disease in which the tissue that lines the uterus grows elsewhere in the pelvic cavity, creating lesions on the ovaries, fallopian tubes, or behind the uterus. An estimated 11% of women in the United States, 6,500,000 in total, have the condition which often leads to chronic pain and infertility.

 

The disease presents in three main forms. Superficial endometriosis is mainly seen on the mucous membrane around the pelvic cavity, while more severe forms are found as cysts within the ovaries called endometriomas and as deep infiltrating endometriosis, which affects the organs near the uterus, like the ovaries, bladder and bowels.

 

In the Utah-based cohort, researchers found that women suffering from more severe types of endometriosis are more likely to develop type I ovarian cancer.

 

“That's where we found a 19-fold increased risk, which compares to the connection between smoking and lung cancer,” said Schliep.

 

“As an epidemiologist, seeing numbers like that is really striking.”

 

In their calculations, they also found that women with any kind of endometriosis have a 4.2-fold risk of developing ovarian cancer compared to those who do not. They also have over 7 times the risk of developing type I ovarian cancer, which is slow to develop but also does not respond well to chemotherapy.

 

The study was published in the Journal of the American Medical Association.