RESUMO
BACKGROUND: This study aimed to evaluate the impact of breast cancer mass screening, which began in 1996 in Loire-Atlantique (France), on the evolution of incidence and characteristics of breast cancer between 1991 and 2002. METHODS: The cancer Registry of Loire-Atlantique recorded characteristics of 9263 incident breast cancers diagnosed between 1991 and 2002. The level of participation to the organised screening program was 48%, thus the screening management structure allowed characterizing 736 cancers discovered by organised screening between 1997 and 2002. RESULTS: The 1991-2002 period was marked by a strong increase of in situ cancer proportion (from 5% at the beginning to 10% at the end of the period) and of standardised incidence rates (from 77 to 103/10(5) and from 4 to 13/10(5) for invasive and in situ cancers, respectively). Incidence was already rising before the beginning of the organised screening program in 1996. During the 1997-2002 period, in spite of steady rates for cancers detected by organised screening, incidence of cancers detected outside organised screening went on increasing. Cancers detected by organised screening were more often of smaller size (33% versus 22% smaller than 10mm) and without lymph node invasion (70% versus 62%). CONCLUSION: A strong increase of breast cancer incidence was observed in Loire-Atlantique, particularly in the organised screening age groups. The persistent increase of in situ cancers for women younger than 50 years old unconcerned by the organised screening program, and also for women of 50-74 years old detected outside the organised screening program suggested a parallel contribution of individual screening. These preliminary results confirm better prognostic factors for cancer detected by organised screening than for others.
