The association between endometriosis and survival outcomes of ovarian cancer: Evidence‑based on a meta‑analysis
Background: Although it is generally recognized that endometriosis was significantly associated with higher risk of ovarian cancer, the association between endometriosis and the cancer survival outcomes is still not clear. This meta‑analysis aims to pool previous studies and to make an update estimate.
Methods: Relevant studies were searched among PubMed, Medline and Embase. Hazard ratio (HR) and the corresponding 95% confidence intervals (CI) of progression‑free survival (PFS) and overall survival (OS) were pooled with generic inverse variance method. The proportion of the low stage and grade tumors (stage: Stage I and II among total; grade: Grade I among total) in endometriosis‑associated ovarian cancer (EAOC) group and in non‑EAOC group were assessed with odd ratio and the corresponding 95% CI.
Results: Endometriosis‑associated ovarian cancer were significantly associated with higher rate of OS in crude analysis (HR: 0.74, 95% CI: 0.63-0.87, P = 0.0003). However, in most of the studies included, the OS benefit was not significant under multivariable survival analysis. EAOC patients generally had early‑stage, low histological grade tumors and younger age compared with non‑EAOC patients. No difference was observed in PFS between the two groups.
Conclusion: The OS benefits associated with endometriosis might be closely related to higher prevalence of patients diagnosed at early‑stage and greater chance of receiving optimal cytoreductive surgery or chemotherapy. Endometriosis should not be viewed as an independent prognostic factor of ovarian cancer.
Key words: Endometriosis, meta‑analysis, ovarian cancer, survival