OBJECTIVE: To compare clinical demographic and prognostic factors as well as overall survival in a nationwide cohort of patients diagnosed with ovarian clear cell carcinoma (oCCC) and high grade ovarian serous adenocarcinoma (oSAC) during 2005 to 2013.

MATERIALS AND METHODS: Population-based prospectively collected data on oCCC (n = 179) and oSAC (n = 2363) cases were obtained from the Danish Gynecological Cancer Database. χ, Fischer or Wilcoxon-Mann-Whitney, multivariate logistic regression, univariate Kaplan-Meier, and multivariate Cox regression tests were used. Statistical tests were 2-sided. P values less than 0.05 were considered statistically significant.

RESULTS: The oCCC cases were significantly younger than oSAC cases. An inverse association between ever smoking and oCCC as compared to oSAC was observed and a significantly higher proportion of oCCC was found to be nulliparous (odds ratio, 0.62; 95% confidence interval, 0.37-0.92).Although more oSAC than oCCC cases diagnosed in stage III or IV were referred to neoadjuvant chemotherapy, a higher proportion of oCCC achieved complete cytoreduction at primary debulking surgery and/or had lymphadenectomy performed; overall survival were poorer among oCCC than oSAC cases in analyses restricted to stages III and IV (odds ratio, 1.87; 95% confidence interval, 1.35-2.61), whereas no difference between early stage oCCC and oSAC was observed.

CONCLUSIONS: The study confirms that demographic features and risk factors differ between oCCC and oSAC cases. Furthermore, our findings confirm that advanced stages of oCCC have a poorer prognosis compared with oSAC probably because of the resistance toward adjuvant chemotherapy. The observed differences highlight the need for subtype-specific research and individualized treatment within ovarian cancer.