ARE INCREASES IN MAMMOGRAPHIC SCREENING STILL A VALID EXPLANATION FORTRENDS IN BREAST-CANCER INCIDENCE IN THE UNITED-STATES

A number of studies have attributed much of the sharp increase in brea st cancer incidence in the United States during the 1980s to the incre ased detection through mammography. The most recent breast cancer data from the US National Cancer Institute's Surveillance, Epidemiology, a nd End Results (SEER) program show that the incidence trend has slowed , while results from the National Health Interview Survey (NHIS) of 19 87 and 1990 indicate that the percentage of women receiving mammograms continues to increase. This phenomenon suggested the need to reassess the relationship between increasingly early detection of breast cance r and overall incidence trends. A polynomial age-cohort model was used to establish the secular trend in incidence rates excluding the impac t of recent increases in detection due to the rising use of mammograph y. Based on the model, the incidence trend in the youngest age group ( 40 to 49 years) would peak and then begin to decline in the early 1980 s, This pattern would manifest itself later in successively older age groups as these younger cohorts age. Breast cancer trends are seen to be generally consistent with the impact of the increased use of mammog raphy when its effect is superimposed upon the background of declining or slowing secular trends. These results support previous reports lin king incidence rates with the increase in screening-mammography.