Objective: Randomised clinical trials with a control arm of non-screened patients are nowadays ethically impossible. The aim of this study was to establish the impact of mammography screening on a non-selected population.
Patients and methods: Between January 1993 and December 2002, 3662 patients were included, 2313 in the screened group and 1349 in the unscreened group.
Results: 55.3% of the screened patients were diagnosed in stage I vs. 26.1% in the non-screened group. The proportion of stage III-IV was 4.6% and 19.8% for the screened and unscreened groups respectively (p<0.001). 48.8% in the screening group were submitted to mastectomy vs. 66.4% of the unscreened patients (p<0.001). Overall survival was superior for the prevalent cases in the screening group, with a relative risk of 0.49, and was not significant for the incident cases.
Conclusions: Diagnosis of breast cancer in the mammography screening programme of the Region of Valencia significantly increases conservative surgery rates and suggests an improvement in survival in prevalent cases. The increased rate of early stages in these patients could be the main reason of this benefit.