Screening caused rising incidence rates of ductal carcinoma in situ of the breast.

The purpose of this study was to examine trends in incidence and detection of ductal carcinoma in situ (DCIS) of the breast in southern Netherlands in the period 1984-2006 and assess the effect of mass screening. All patients with primary DCIS registered between 1984 and 2006 in the population-based Eindhoven Cancer Registry were included (n = 1,767). These data were linked to data from the population-based screening programme. The incidence of DCIS of the breast increased from 3/100,000 to almost 34/100,000 person-years in women aged 50-69 years in southern Netherlands since 1984. Mass screening was responsible for this increase. A stable 60% of DCIS was screen-detected. Over 11% of breast cancer patients have DCIS. In conclusion, the incidence of DCIS increased markedly in southern Netherlands with a clear effect of mammography screening since 1992.