Is the presence of endometriosis associated with a survival benefit in pure ovarian clear cell carcinoma?

The purpose of this study was to compare the prognoses of women with pure ovarian clear cell carcinoma (OCCC) arising from endometriosis to those of women with pure OCCC not arising from endometriosis treated in the same manner. A dual-institutional, retrospective database review was performed to identify patients with pure OCCC who were treated with maximal or optimal cytoreductive surgery (CRS) followed by paclitaxel/carboplatin chemotherapy between January 2006 and December 2016. Patients were divided into two groups according to the detection of cancer arising in endometriosis or not, on the basis of pathological findings. Demographic, clinicopathological, and survival data were collected, and prognosis was compared between the two groups. Ninety-three women who met the inclusion criteria were included. Of these patients, 48 (51.6%) were diagnosed with OCCC arising in endometriosis, while 45 (48.4%) had no concomitant endometriosis. OCCC arising in endometriosis was found more frequently in younger women and had a higher incidence of early stage disease when compared to OCCC patients without endometriosis. The 5-year overall survival (OS) rate of the patients with OCCC arising in endometriosis was found to be significantly longer than that of women who had OCCC without endometriosis (74.1 vs. 46.4%; p = 0.003). Although univariate analysis revealed the absence of endometriosis (p = 0.003) as a prognostic factor for decreased OS, the extent of CRS was identified as an independent prognostic factor for both recurrence-free survival (hazard ratio (HR) 8.7, 95% confidence interval (CI) 3.15-24.38; p < 0.001) and OS (HR 11.7, 95% CI 3.68-33.71; p < 0.001) on multivariate analysis. Our results suggest that endometriosis per se does not seem to affect the prognosis of pure OCCC.