Role of endometriosis as a prognostic factor for post-progression survival in ovarian clear cell carcinoma

The clinical significance of coexistence of endometriosis (EM) in ovarian clear cell carcinoma (CCC) has not yet been determined. The aim of the present study was to analyze the correlation of endometriosis with clinicopathological factors in CCC. The cases with CCC that received primary debulking surgery at the present hospital between 1990 and 2013 were identified. Retrospective analysis was conducted to evaluate the association between complications with EM and clinicopathological features in CCC. Of the 105 cases enrolled in the study, 45 cases were complicated with EM, and 60 cases did not have EM (non-EM). The patients with EM were diagnosed at a younger age (P=0.03), and at earlier stages (P<0.01) compared with non-EM cases. Although there was no significant difference of progression-free survival (P=0.36), complications with EM were identified as an independent prognostic factor for overall survival (OS; P<0.01) by multivariate analysis. A total of 48 patients (45.7%) developed recurrence: 18 patients in EM-group and 30 patients in non-EM group. There were no significant differences of clinicopathological factors in the treatment at recurrence between both groups. Recurrent cases in EM had significantly worse post-progression survival (PPS) compared with recurrent non-EM group (P<0.01). Multivariate analysis for PPS demonstrated that complications with EM (P<0.01) were identified as a worse prognostic factor. In CCC, the complication with EM was identified as a significant worse prognostic factor for PPS in recurrent cases. Additionally, EM was significantly associated with OS in all cases with CCC. Novel treatment strategies are therefore necessary for recurrent CCC, particularly for cases exhibiting EM.