Ovarian cancer risk differs based on endometriosis subtype

Women with endometriosis were 4.20 times more likely to develop ovarian cancer than those without it, while ovarian endometriomas and/or deep infiltrating endometriosis was associated with a 9.7-fold greater risk of ovarian cancer compared with controls, a cohort study found.

To determine how endometriosis subtypes influence ovarian cancer risk, researchers matched 78,893 women diagnosed with endometriosis between 1992 and 2019 to women without endometriosis 1:5 using data from the Utah Population Database. They used electronic health records to identify and categorize cases as superficial endometriosis, ovarian endometriomas, deep infiltrating endometriosis, or other. Average patient age at endometriosis diagnosis was 36 years; 597 women developed ovarian cancer during the study window. Findings were published by JAMA on July 17.

Most endometriosis cases were superficial peritoneal endometriosis (49.8%), followed by ovarian endometriomas (24.1%), deep infiltrating endometriosis (1.3%), and ovarian endometriomas and concurrent deep infiltrating endometriosis (1.7%). Compared with women without endometriosis, those with it had a significantly higher risk of ovarian cancer overall (adjusted hazard ratio [aHR], 4.20 [95% CI, 3.59 to 4.91]; adjusted risk difference [aRD], 9.90 [95% CI, 7.22 to 12.57]) and type I ovarian cancer (aHR, 7.48 [95% CI, 5.80 to 9.65]; aRD, 7.53 [95% CI, 5.46 to 9.61]). Patients with deep infiltrating endometriosis and/or ovarian endometriomas had the highest risk of all ovarian cancers (aHR, 9.66 [95% CI, 7.77 to 12.00]; aRD, 26.71 [95% CI, 20.01 to 33.41]) and type I ovarian cancer (aHR, 18.96 [95% CI, 13.78 to 26.08]; aRD, 19.57 [95% CI, 13.80 to 25.35]). Patients with endometriosis were more likely to be nulliparous and to have undergone a hysterectomy than those without endometriosis.

One limitation to the study was the possibility of misclassification of endometriosis due in part to lack of a biomarker for diagnosis. Ovarian cancer histotypes may have also been misclassified, the study authors noted. Data on two medications commonly used by patients with endometriosis were also unavailable.

"By quantifying the strong associations between deep infiltrating endometriosis and/or ovarian endometriomas subtypes and ovarian cancer risk, this study identified a population that may benefit from ovarian cancer screening or more aggressive prevention strategies," the researchers wrote.

An accompanying editorial commended the study but pointed out the researchers did not provide a clear and consistent definition of deep infiltrating endometriosis, which may preclude drawing clinical recommendations from the observations.

"Molecular assessment of women with endometriosis and ovarian cancer, compared with women with endometriosis without ovarian cancer, may facilitate the identification of women at higher risk. Ultimately, characterizing these differences could support consideration for a more prescriptive surveillance recommendation or possible strategies for risk reduction," the editorialist concluded.