EXPLORING TIME TRENDS IN CANCER INCIDENCE

We examined incidence time-trends for lung, stomach, intestinal, prostate, and breast cancer among Whites diagnosed in the United States between 1973 and 1987. For each sex and five-year age group, we modeled cancer incidence as a log-linear function of diagnosis-year to permit extrapolation over time and simple summarization of trends. Comparisons with nonparametric estimates show that, except for breast cancer, the model performs well. Plots of the annual percent change in incidence cf age illustrate the way in which time trends depend on age. Between 1973 and 1987, stomach cancer incidence decreased by about two percent per year. The annual change in lung cancer incidence progressed from a two to three percent decrease in persons under age 40 to an increase of two percent in men and eight percent in women by age 80. Intestinal cancer incidence decreased annually by as much as three percent in persons under age 50, remained constant in women aged 50 to 74, and otherwise increased about one percent per year. The annual increase in prostate cancer incidence declined from about six percent in men under age 40 to about two percent in men over age 80. After a surge in female breast-cancer diagnoses in 1974, the annual increase in incidence between 1980 and 1987 stabilized at four to six percent.