Changes in breast cancer incidence and stage distribution in Modena, Italy: the effect of mammographic screening program.

Objective: Assessing changes in breast cancer (BC) incidence and stage distribution in the District of Modena, Italy, during the period 1992-1998, and their relationship to a mammographic screening program launched in 1995. Methods: Demographic, clinical, and pathological data of all BC cases reported to the population-based Modena Cancer Registry between 1992 and 1998 were collected and linked to the screening database. Results: A total of 3429 women were diagnosed with BC in the District of Modena between 1992 and 1998. In this period the incidence rate increased by 15.7% (from 134.3 in 1992 to 155.4 per 100,000 in 1998). The increase began in 1995 and exclusively included women aged 50-69; the incidence rose by 30.4%. Moreover, the rise was confined to early tumors, with more than half (54%) of all cases reported in 1998 diagnosed as stage 0 or I disease, compared with 42% in 1992. Screen-detected tumors were significantly smaller (13.2 mm) than other tumors diagnosed in women aged 50-69 (18.5 mm), with 46% of screen-detected tumors smaller than 10 mm. Overall, a decline in the average tumor diameter was shown (from 20.2 mm in 1992-1994 to 18 mm in 1996-1998). Conclusions: Our data confirm that mammographic screening leads to an increase in the incidence of early-stage BC cancers.