The early impact of the breast cancer screening programme in the city of Florence: methods of evaluation and first results (1990-1996)

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Since 1990, the female population of Florence aged 50-69 years (n = 59 601) has been invited to have a 2-view, high quality mammogram every 2 years. As of December 31, 1996, the first and second round were completed and the third was under way. The analysis is based on the breast cancer staging with or without the screening programme. The total women-years in the study period were 419 179; 129 603 before the invitation. Case incidence in the not-yet-invited women group are used as the estimate of the underlying incidence. Two-hundred and twenty-eight breast cancer cases were detected at the first screening round. The total number of cases expected in the invited women population on the basis of the underlying incidence was 1051. There were 1216 observed in the 289 576 women-years group, with an excess of 165 breast cancer cases (16%). All incident cases were staged according to TNM and Grade. An approach to the analysis based on the 'unbiased set' (Day and Duffy, 1999) will be presented and, in this subset, a reduction of the advanced carcinomas (Stage II+) from 57% to 42% was estimated. Detailed data of the incidence over time, stage distribution and methodological issues will be discussed.