The relation between endometriosis and ovarian cancer - a review

Background: Endometriosis is known to harbor characteristics substantiating its possible role as a precursor of ovarian cancer.

Objective: To assess the quality of the literature regarding the association between endometriosis and ovarian cancer and to estimate the extent of this relation.

Methods: An electronic literature search was conducted in PubMed and 1112 articles dealing with the relation between endometriosis and ovarian cancer were identified. Original articles based on case-control studies, cohort studies and cross-sectional studies were included. Studies consisting of populations with self-reported endometriosis were excluded, as were articles with fewer than 20 cases of ovarian cancer. Twenty-eight studies underwent detailed quality assessments based on the checklists developed by the Scottish Intercollegiate Guidelines Network (SIGN). Meta-analyses were conducted on selected subgroups of ovarian cancer with coexisting endometriosis.

Results: None of the 28 studies was given the highest possible rating using the SIGN checklists. The risk of ovarian cancer in women with endometriosis was reported to be a standardized incidence ratio of 1.43-8.95, a rate ratio of 1.6-2.88, an odds ratio of 1.34, with a prevalence of ovarian cancer in 2.0-17.0% of women with endometriosis. Conversely, the prevalence of endometriosis in women with ovarian cancer ranged from 3.4 to 52.6%. Meta-analysis results were weakened by heterogeneity.

Conclusion: There is sufficient evidence to conclude that there is an increased risk of developing clear-cell and endometrioid epithelial ovarian cancer for women with histologically verified endometriosis. Nonetheless, prospective cohort studies assessing the relation between endometriosis and ovarian cancer will increase knowledge in this field.