Histology-specific long-term trends in the incidence of ovarian cancer and borderline tumor in Japanese females: A population-based study from 1983 to 2007 in Niigata

Aim: The histology-specific long-term trends in the incidence of ovarian cancer and borderline tumors in Japanese women were examined, based on data from the population-based cancer registry in Niigata, Japan. Material and Methods: Data were obtained from the Niigata Gynecological Cancer Registry, which covered the entire female population in Niigata prefecture, Japan, during the period from 1983 to 2007. Results: A total of 3134 females with epithelial ovarian cancer, including borderline tumor cases, were diagnosed between 1983 and 2007. The age-standardized rates (ASRs) of both ovarian cancer and borderline tumors have steadily increased, with significant changes in ovarian cancer in all age groups, and borderline ovarian tumors in subjects aged <50. The ASRs of endometrioid adenocarcinoma showed a steady increasing trend, and those of clear cell and mucinous adenocarcinomas showed significant increasing trends in the total population. The ASRs of clear cell, mucinous, and endometrioid adenocarcinomas in the 50+ age group were significantly increased, especially the incidence of clear cell adenocarcinoma, which strikingly increased by approximately threefold from 1.2 (1983-1989) to 3.5 (2000-2007) per 100 000 females. Conclusion: This prefecture-wide study showed the practical trends in ovarian cancer and borderline tumors in Japanese females. The incidence of ovarian cancer has steadily increased, with significant increases in the incidence of clear cell and mucinous adenocarcinomas in the total population during the past two decades. Because of the poor response rate of these histological subtypes to platinum-based regimens, novel treatment approaches should be adopted to improve the prognostic outcome in patients with ovarian cancer in Japan.