TRENDS IN CERVICAL AND BREAST-CANCER IN ICELAND - A STATISTICAL EVALUATION OF TRENDS IN INCIDENCE AND MORTALITY FOR THE PERIOD 1955-1989, THEIR RELATION TO SCREENING AND PREDICTION TO THE YEAR 2000

The time trends in incidence and mortality from cervical cancer and breast cancer in Iceland, from 1955 to 1989, were analyzed by fitting curvilinear regressions to the age-standardized rates. The effect of the screening was evaluated by comparing the curvature of the fitted regression lines and changes in screening activity. The incidence and mortality rates for both cancer types were predicted up to the year 2000. At the commencement of cervical cancer screening in 1964, both the incidence and mortality rates were on the increase. After 1970, both rates decreased significantly. Assuming that regular attendance at screening will be 85%, it is predicted that the incidence and mortality rates will level out at about 7.5 and 2 cases per 100,000 women per year, respectively, by the year 1995 and remain at that level. The incidence of breast cancer has increased steadily since 1955. A sharp rise has been observed since 1987, due to screening with mammography. The mortality rate has shown small but significant fluctuations with time. The incidence rate is predicted to increase at the same rate as before 1987 (i.e. at I.I cases per 100,000 women per year), but at a slightly higher level and is predicted to reach 84 cases per 100,000 women per year by the year 2000. Breast cancer mortality is predicted to decrease to about 17 cases per 100,000 women per year by 1995 and to remain at that level.