BREAST-CANCER IN EAST-ANGLIA - THE IMPACT OF THE BREAST SCREENING-PROGRAM ON STAGE AT DIAGNOSIS

Objectives-To assess the impact of the National Health Service breast screening programme on overall and stage-specific incidence of breast cancer in East Anglia; also, to predict the magnitude of the screening induced reduction in breast cancer mortality. Setting-Women resident in East Anglia aged 50-69, diagnosed between 1976 and 1995 Methods-Com parison of numbers and incidence of breast cancer by age, stage, and m ode of detection; investigation of relative contributions of advanced (stages II, III, and IV) cancers to total incidence by detection mode; estimation of the reduction in advanced cancer incidence. Results-The re has been a large increase in early stage incidence in the age group 50-64 targeted by the screening programme. By 1995, the estimated dec rease in advanced cancer incidence was between 7 and 19%. In 1995, of all breast cancers arising in the age group 50-69 years, 33% were scre en detected, 27% were interval cancers, 15% were in non-attenders, 9% were in lapsed attenders, 7% occurred before invitation, and 4% arose in women outside the birth year range for invitation. Of the advanced cancers diagnosed in 1995, 31% were interval cancers, 20% were screen detected, 19% were in nonattenders, 12% were in lapsed attenders, 8% o ccurred before invitation, and 4% presented in women outside the birth year range for invitation. Conclusions-Screening has brought about a large increase in detection of early stage cancers. This increase has not get been fully matched by a corresponding deficit in advanced canc ers, possibly because the full effect of screening has not yet been ac hieved. Reducing the proportion of interval cancers is necessary to in crease the effect of screening on mortality.