Endometriosis Raises Ovarian Cancer Risk, but Patients Who Develop It Have Better Survival Outcomes

Women with endometriosis have an elevated risk of developing epithelial ovarian cancer, but, when they do develop it, they tend to fare significantly better than patients without endometriosis, according to a new systematic review and meta-analysis published in the Journal of Minimally Invasive Gynecology.¹

The analysis, which pooled data from 67 studies and more than 500,000 women, offers a comprehensive look to date at the relationship between endometriosis and ovarian cancer risk, tumor characteristics, and survival.

How the Study Was Conducted

The ENDOCANCER review, conducted by researchers across multiple Italian institutions, searched PubMed and Google Scholar for eligible studies through August 2025. Of the identified studies, 42 examined cancer risk in women with endometriosis, while 25 focused on survival outcomes in women diagnosed with endometriosis and ovarian cancer. All included studies were observational in design, published between 1997 and 2025.

Researchers used random-effects models to generate pooled ORs, HRs, and standardized incidence ratios (SIRs). They also conducted sensitivity analyses to test the robustness of findings. Rather than combining different risk metrics into a single pooled estimate, the authors stratified results by the type of risk measure used, improving comparability across studies and enabling a more precise evaluation of the relationships.

Trends in Endometriosis-Associated Ovarian Cancer (EAOC)

Across all risk metrics, endometriosis was associated with a statistically significant increase in ovarian cancer risk, with a pooled OR of 1.82, an HR of 3.03, and an SIR of 1.62. However, absolute incidence across groups remained low, roughly 0.7% to 1.5%, underscoring that ovarian cancer is still a rare outcome in this population.

When cancer did develop, patients with EAOC were distinctly different from those without endometriosis. They were younger, more often premenopausal, and more likely to present with early-stage and lower-grade tumors. Clear cell and endometrioid histotypes predominated in the EAOC group, while serous and mucinous subtypes were more common in the non-EAOC cohort. Preoperative CA125 was also significantly lower in patients with EAOC.

Interestingly, overall survival was significantly better in patients with EAOC (HR, 0.48), and both recurrence and mortality were significantly lower. However, platinum resistance rates were similar between groups.

"EAOC exhibits specific characteristics: younger age at diagnosis, higher likelihood of premenopausal status, earlier [International Federation of Gynecology and Obstetrics] stage, lower tumor grade, and predominance of clear cell and endometrioid histotypes,” the authors wrote. “These features contribute to the significantly improved overall survival and lower recurrence and mortality observed in EAOC compared with non-EAOC."

Why This is Important for Clinicians

For clinicians managing patients with endometriosis, this meta-analysis offers a clearer, evidence-grounded framework: acknowledge the elevated relative risk, contextualize the low absolute risk carefully, and recognize that when ovarian cancer does develop in this population, it tends to behave less aggressively and respond to treatment more favorably.

Personalized counseling, targeted surveillance, and continued investment in molecular research are the path forward. It also adds important prognostic context, as EAOC may be a biologically distinct entity, not simply ovarian cancer that happens to co-occur with endometriosis due to the unique clinicopathologic features and improved survival.

More Prospective Studies Are Needed to Confirm and Expand on Findings

The authors called for prospective studies using standardized diagnostic criteria; clearer temporal data establishing when endometriosis precedes cancer; and subgroup analyses by endometriosis phenotype (ovarian, peritoneal, or deep infiltrating).

Identifying molecular biomarkers of malignant transformation, such as the ARID1A mutations already implicated in the endometriosis-to-cancer continuum, also remains a priority.² Determining whether long-term hormonal suppression modifies EAOC risk is another unanswered question with real clinical relevance.¹

References

1. Piacenti I, Tius V, Gomba B, et al. Risk, prevalence and survival outcomes of ovarian cancer in women with endometriosis: the ENDOCANCER systematic review and meta-analysis. J Minim Invasive Gynecol. Published online May 6, 2026. doi:10.1016/j.jmig.2026.04.021
2. Steinbuch SC, Lüß AM, Eltrop S, Götte M, Kiesel L. Endometriosis-associated ovarian cancer: from molecular pathologies to clinical relevance. Int J Mol Sci. 2024;25(8):4306. doi:10.3390/ijms25084306