Non-epithelial ovarian cancer in Denmark - Incidence and survival over nearly 40 years.

OBJECTIVE

To examine trends in incidence and survival of non-epithelial ovarian cancer in Denmark over nearly 40 years, using nationwide, population-based cancer registry data.

METHODS

From 1978 to 2016, we identified the non-epithelial ovarian cancer cases among all ovarian malignancies in the Danish Cancer Registry. Age-specific incidence rates, age-standardized incidence rates, and average annual percentage change (AAPC) were estimated with 95% confidence intervals (CIs). Overall and 5-year relative survival analyses were conducted and supplemented with Cox regression to explore the effect of different characteristics on overall mortality.

RESULTS

A total of 720 non-epithelial ovarian cancers were identified, corresponding to 3.4% of all ovarian malignancies. The majority of non-epithelial ovarian cancers were germ cell tumors (49.9%) and sex cord-stromal tumors (38.6%). The age-standardized incidence rate of germ cell tumors was stable over the study period, ranging between 0.33 and 0.39 per 100,000 woman-years. In contrast, the age-standardized incidence rate of sex cord-stromal tumors declined from 0.30 (1978-1987) to 0.09 (2008-2016) per 100,000 woman-years (AAPC = -5.15%; 95% CI: -7.29, -2.96). The 5-year relative survival of germ cell tumors and sex cord-stromal tumors was 94% and 79%, respectively, in the most recent period (2008-2011). Cox regression showed that overall mortality was associated with calendar year, age, and stage.

CONCLUSIONS

The incidence of germ cell tumors was stable over calendar time, whereas the incidence of sex cord-stromal tumors decreased significantly. Non-epithelial ovarian cancer overall mortality has decreased during the study period and this could not be explained by taking stage and age at diagnosis into account.