Epidemiology of choriocarcinoma in Finland, 1953 to 1999.
Choriocarcinoma is a rare tumor with remarkable differences in the incidence in various parts of the world. The available data do not elucidate recent time trends in the incidence of the disease in Western countries. We studied the epidemiology of choriocarcinoma in Finland over a period of 47 years. Incidence rates for choriocarcinoma from 1953 to 1999, according to the population-based Finnish Cancer Registry, were calculated per number of deliveries, obtained from the National Research and Development Center for Welfare and Health. Standardized incidence ratios (SIRs) for the years 1971 through 1995 for women born between 1906 and 1945 were calculated by occupation taken from the 1970 Population Census. The incidence of choriocarcinoma was 40/10(6) deliveries for the study period 1953-1999 as a whole. The respective incidence rate calculated per female population and adjusted for age to the world standard population was 1.3/10(6). The incidence, per number of deliveries, was remarkably higher in women above 40 years as compared to younger women. There was a decline in the incidence of the disease in women between 25 and 39 years of age from 53/10(6) deliveries in 1953-1984 to 26/10(6) deliveries in 1985-1999. High occupation-specific risks were observed for nurses (SIR 7.8; 95% confidence interval 2.1-20) and agricultural workers (SIR 11; 95% confidence interval 1.4-40). The incidence of choriocarcinoma in Finland is similar to that reported earlier for other Western countries. The recent decline in the incidence of the disease, the enormous increase in the risk among old fertile women, and clustering of cases to certain occupations should be targets of future studies.