Ovarian cancer incidence and survival by histologic type in Osaka, Japan

The incidence of ovarian cancer among Japanese has increased since the 1970s. Histologic diversity is a characteristic of this cancer. However, there has been no population-based study made on the incidence and survival by histologic type. Osaka Cancer Registry's data was used for incidence and survival analyses of ovarian cancer by histologic type in this study. Seven thousand one hundred sixty-seven incident cases were registered during the period 1975 to 1998. According to the IARC's histologic classification, types of ovarian cancer were classified into five categories. Survival analysis was restricted to the reported 2431 cases who lived in Osaka Prefecture (except for Osaka City) and were diagnosed in 1975-1994, since active follow-up data on vital status 5 years after the diagnosis were available. The age-standardized incidence rate of ovarian cancer increased from 4.0 to 5.4 per 100,000 women (standard: world population) in Osaka during the period 1975-1998. Carcinoma, the major histologic category, also increased (from 3.4 to 4.8 per 100,000 women), while sex cord-stromal tumors decreased after 1980 and germ cell tumors remained stable. The 5-year relative survival was 36.4% for ovarian cancer patients diagnosed in 1975-1994. The survival for carcinoma was 38.3%, which was lower than that in sex cord-stromal tumors or germ cell tumors (55.3% and 58.6%, respectively). The increase in the incidence of ovarian cancer was caused by the increase in carcinoma. The relative 5-year survival of ovarian cancer improved over the period, but was different by histologic type.