The incidence of borderline ovarian tumors in Israel: A population- based study

BACKGROUND. In hospital-based studies, one-eighth of ovarian cancers have been considered borderline ovarian tumors (BOTs). Population-based data regarding the incidence of BOTs are lacking in the international literature. The authors objectives were to measure the incidence of BOT in Israel and compare rates among ethnic groups (based on ethnic group and country of birth) for the years 1985-1993. METHODS. The authors analyzed data reported to a nationwide cancer registry. Population estimates by subpopulation were derived from census and intercensus estimates, which were based on an updated population registry. RESULTS. The age-adjusted standard rate (ASR) for the entire population was 10.6 per million (95% confidence interval [CI], 9.2- 12.0) for the period 1985-1993. Significant differences in ASR were observed among ethnic subgroups, with the lowest incidence among non-Jews (ASR, 5.0 per million; 95% CI, 0.7-9.3) and the highest among new immigrants from the former Soviet Union (FSU) who had been arriving since 1989 (ASR, 22.7 per million; 95% CI: 14.2-31.3). Between the periods 1985-1989 and 1990-1993, the ASR for Jews nearly doubled (rate ratio, 1.86; 95% CI, 1.1-2.5). This near- doubling was influenced, but not wholly accounted for, by the immigration from FSU and was observed in all ethnic subgroups. CONCLUSIONS. The variations in the incidence rates of BOT among ethnic groups may be related to differences in fertility patterns, use of fertility drugs, and genetic predisposition. The pattern of near-doubling in rates may reflect biases caused by increased detection or shifts in the classification of ovarian tumors; if they are real, a biologic explanation is needed.