Endometriosis Typology and Ovarian Cancer Risk

Ovarian, breast, and endometrial cancers are known to be associated with endometriosis. This study was designed to assess associations between endometriosis and its subtypes with the overall incidence of ovarian cancer and the incidence of ovarian cancer by histologic type. This study used data from the Utah Population Database to conduct a retrospective cohort study, which included data collected between 1992 and 2019. Inclusion criteria were age 18 to 55 years and 1 or more endometriosis diagnosis. Endometriosis was divided into 5 subtypes, including superficial peritoneal endometriosis, ovarian endometriomas, deep infiltrating endometriosis, ovarian endometriomas, and concurrent deep infiltrating endometriosis. Control patients were age matched to women without a diagnosis of endometriosis. Final analysis included 39,277 patients with superficial peritoneal endometriosis, 18,977 with ovarian endometriomas, 1028 with deep infiltrating endometriosis, and 1374 with ovarian endometriomas and concurrent deep infiltrating endometriosis, as well as 18,237 classified as “other.” Individuals with a diagnosis of endometriosis had an increased risk for the development of all ovarian cancer types when compared with those without endometriosis (overall risk, 4.20; 95% confidence interval [CI], 3.59–4.91). The elevated risk was greatest in patients with deep infiltrating endometriosis and/or ovarian endometriomas (adjusted hazard ratio [aHR], 9.66; 95% CI, 7.77–12.00). The strongest association documented was between deep infiltrating endometriosis and/or ovarian endometriomas with type I ovarian cancer (aHR, 18.96; 95% CI, 13.78–26.08). Sensitivity analyses removing parity showed even greater elevations in risk for all subtypes of cancer. These results indicate a greatly increased risk for the development of ovarian cancer in individuals with an endometriosis diagnosis, although the magnitude of the risk elevation was variable based on the subtype of endometriosis. The associations in this study were stronger than shown in previous research, possibly due to many previous studies relying on self-reported diagnosis of endometriosis rather than medical documentation. Studies from other countries using similar medical data have reported results similar to this study, although no studies have yet parsed the associations by both endometriosis and cancer subtype. Future research should focus on consistent diagnostic methods for endometriosis, including asymptomatic individuals with endometriosis, and minimizing inaccuracies in data surrounding demographics and/or reporting errors.