Trends in incidence of borderline ovarian tumors in Denmark 1978-2006

Abstract

Objective: To examine period-, age- and histology-specific trends in the incidence rate of borderline ovarian tumors in Denmark in 1978-2006.

Design: Register-based cohort study.

Setting: Denmark 1978-2006.

Population: 5079 women diagnosed with a borderline ovarian tumor in at least one of two nationwide registries (4312 epithelial tumors and 767 non-epithelial/unspecified tumors).

Methods: Estimation of overall incidence rates and period-, age- and histology-specific incidence rates. Age-adjustment was done using the World Standard POPULATION. To evaluate incidence trends over time, we estimated average annual percentage change and 95% confidence intervals (CI) using log-linear Poisson models.

Main outcome measures: Age-standardized and age-specific incidence rates and average annual percentage change.

Results: The incidence of epithelial borderline ovarian tumors increased from 2.6 to 5.5 per 100,000 women-years between 1978 and 2006, with an average annual percentage change of 2.6% (95% CI: 2.2-3.0). The median age at diagnosis was 52 years. Women 40 years or older had a higher average annual percentage change than women younger than 40 years. Most tumors were mucinous (49.9%) and serous tumors (44.4%). Women with mucinous tumors were younger at diagnosis (50 years) compared with women with serous tumors (53 years). Women with serous tumors had a higher average annual percentage incidence change than women with mucinous tumors.

Conclusions: The incidence rate of borderline ovarian tumors increased significantly in Denmark in 1978-2006. In line with results for ovarian cancer, Denmark had a higher incidence rate of borderline ovarian tumors compared with the other Nordic countries in 1978-2006.