Women with more severe forms of endometriosis have a nearly 10-fold higher risk of ovarian cancer

Women with a history of endometriosis have a nearly 4-fold higher risk of ovarian cancer than those without one, and those with more severe forms of the disease, namely ovarian endometriomas and deep infiltrating endometriosis, have a nearly 10-fold higher risk, according to a population-based cohort study published in JAMA.¹

The study also found that women with any kind of endometriosis (e.g., low-grade serous, clear cell, mucinous, and endometrioid) had more than 7 times the risk of developing type 1 ovarian cancer. Those with deep infiltrating endometriosis or ovarian endometriomas had nearly 19 times the risk of developing type 1 ovarian cancer.

“As an epidemiologist, seeing numbers like that is really striking,” says Karen Schliep, PhD, MSPH, associate professor in the Department of Family and Preventive Medicine at the University of Utah Health and senior author of the study. In a press release, she compared the 19-fold increased risk to the risk for lung cancer seen with smoking.²

Schliep and her colleagues used data from the Utah Population Database to assess the association of endometriosis with the incidence of ovarian cancer, overall and by subtype, as well as the associated ovarian cancer histotype. Women with a history of endometriosis were identified through electronic health records and the cases then categorized by type (superficial endometriosis, ovarian endometriomas, deep infiltrating endometriosis, or other). The retrospective cohort included nearly 79,000 women with endometriosis matched 1:5 with women without endometriosis.

A total of 597 women developed ovarian cancer between 1992 and 2019, as recorded in the Utah Cancer Registry; these cancers included high-grade serous carcinoma, low-grade serous carcinoma, endometrioid mucinous carcinoma, clear cell carcinoma, and carcinosarcoma. Among the women without a history of endometriosis, ovarian cancers were evenly distributed among these most common histotypes. Overall, all ovarian cancer histotypes were more common in the women with a history of endometriosis.

“This study confirms an elevated risk of epithelial ovarian cancer in patients with a history of endometriosis, mainly due to an increased risk of non-high grade serous histologic subtypes, including endometrioid and clear cell carcinomas,” says Kari L. Ring, MD, a gynecologic oncologist at UVA Health.

Dr Ring calls it “interesting” that the highest risk for ovarian cancer was found in patients with ovarian involvement of endometriomas and deep infiltrating disease. “This raises several questions, including whether advanced endometriosis represents progression along the continuum of the malignant transformation of endometriosis or whether more advanced disease may have a higher risk of residual endometriosis following surgical intervention,” she says.

Dr Ring says that the findings underscore the need for physicians to have “an informed discussion [with their patients] of the risks and benefits of oophorectomy at the time of surgical intervention for endometriosis that includes a discussion of the possible risk of ovarian cancer, especially for patients with known deep infiltrating lesions and ovarian involvement.”