Are increases in mammographic screening still a valid explanation for trends in breast cancer incidence in the United States?

A number of studies have attributed much of the sharp increase in breast cancer incidence in the United States during the 1980s to the increased detection through mammography. The most recent breast cancer data from the US National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program show that the incidence trend has slowed, while results from the National Health Interview Survey (NHIS) of 1987 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 cancer and overall incidence trends. A polynomial age-cohort model was used to establish the secular trend in incidence rates excluding the impact of recent increases in detection due to the rising use of mammography. 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 1980s. 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 mammography when its effect is superimposed upon the background of declining or slowing secular trends. These results support previous reports linking incidence rates with the increase in screening-mammography.