Epidemiologic features of borderline ovarian tumors in California: a population-based study

Borderline ovarian tumors (BOT) became no longer reportable in 2001, and few registries still collect information on these still poorly understood tumors. This study's objective was to describe epidemiologic features, trends, and survival of BOTs compared with those of low-grade (LG) and high-grade (HG) epithelial ovarian cancer (EOC) in the large and diverse population of California.

Data from the California Cancer Registry were used to examine demographic and tumor characteristics among women diagnosed with BOT (n = 9,786), LG-EOC (n = 3,656), and HG-EOC (n = 40,611) from 1988 to 2010. Annual percent changes in BOT and LG-EOC incidence rates were estimated using Joinpoint regression; 5-year relative survival was calculated for both BOTs and LG-EOCs by age, race/ethnicity, and histology.

Age-adjusted incidence rates of BOT in 2009 were 3.1, 2.3, 2.2, and 1.4 per 100,000 among whites, Latinas, African Americans, and Asian/Pacific Islanders, respectively. Incidence rates for LG-EOC decreased by 2.2 % per year; rates for BOT increased by 7.3 % per year until 1993, remained unchanged until 2006, and seemed to decline thereafter. Compared with LG-EOCs, BOTs were diagnosed in higher frequency among Latinas, at younger age, and were more likely to affect only one ovary. Overall, 5-year relative survival for BOT was 98.9 %; among women diagnosed with stage IV BOT, survival was 77.1 %.

In this study, differences between BOTs and LG-EOCs were marked but varied substantially by histologic subtype and were far less dramatic than differences between BOTs and HG-EOCs. Findings underscore the importance of understanding these enigmatic tumors.