Retrospective cohort study of the associations of endometriosis subtypes with incidence of ovarian cancer

Endometriosis has been associated with an increased risk of ovarian cancer; however, the associations between endometriosis subtypes and ovarian cancer histotypes have not been well-described. A population-based cohort study using data from the Utah Population Database found that women with endometriosis had a 4.2-fold higher ovarian cancer risk than those without endometriosis (aHR 4.20; 95% CI 3.59-4.91). Women with ovarian endometriomas and/or deep infiltrating endometriosis, compared with no endometriosis, had 9.7-fold higher risk (aHR 9.66; 95% CI7.77-12.00). Associations between endometriosis subtypes and ovarian cancer histotypes were much greater for type I (endometrioid, clear cell, mucinous, and low-grade serous) compared with type II (high-grade serous) ovarian cancers. The authors conclude that women with endometriosis, especially more severe subtypes, have a markedly increased ovarian cancer risk and may be an inportant population for targeted cancer screening and prevention studies.