Clinical Characteristics Of Clear Cell Ovarian Cancer: A Retrospective Multicenter Experience Of 308 Patients In South Korea.

e17062 Background: Clear cell ovarian cancer is rare, accounts for about 3-10% of epithelial ovarian carcinoma, and is known to be associated with endometriosis. This tumor type has poor prognosis due to inherent chemoresistance. We investigated clinical characteristics and prognostic factors of clear cell ovarian cancer in South Korea. Methods: We reviewed the medical records of 308 patients with clear cell histology ovarian cancer who underwent debulking surgery from 21 institutions in South Korea between 1995 and 2015. Results: Mean age was 51 years (range, 25-81) and 194 patients (63.7%) had stage I disease, 34 (11.1%) had stage II, 66 (21.6%) had stage III, and 11 (3.6%) had stage IV. 107 patients (34.9%) had endometriosis. 9 patients (2.9%) received neoadjuvant chemotherapy, 248 (80.5%) received postoperative chemotherapy, and among them, 238 (96%) received taxane-platinum chemotherapy. 275 patients (89.3%) achieved optimal debulking. 112 patients (37%) had recurrence, 182 (59.1%) was disease-free, and 12 (3.9%) lost follow up. Median value of CA-125 was 72.34 U/ml (range, 1.9-8930), 45.7 in stage I, 98.9 in stage II, 192.1 in stage III, and 634.8 in stage IV. 1-year, and 3-year rate of disease-free survival (DFS) was 70%, and 63%, respectively. 1-yr DFS rate was 90% in stage Ia and Ib, 88% in stage Ic and II, and 60% in stage III and IV. According to the same stage grouping, 3-year DFS rate was 82%, 70%, and 40%, respectively. Overall survival (OS) rate at 1 year was 97%, 99%, and 90%, and 97%, 96%, and 88% at 3 year. Multivariate analysis revealed optimal debulking (HR 6.62, p < 0.001) as a significant prognostic factor for DFS. Among the 94 patients with early stage (Ia and Ib), 17 patients (18.1%) received adjuvant chemotherapy, and there was no significant difference in DFS according to adjuvant chemotherapy (log rank p = 0.57). Conclusions: In patients with clear cell ovarian cancer, optimal debulking surgery was associated with improved DFS. And the role of adjuvant chemotherapy in early stage clear cell ovarian cancer is elusive and needs further study.