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More than a decade ago, a mammography screening programme for women aged 50–69 years was initiated in the Netherlands. Our aim was to assess the effect of this programme on breast-cancer mortality rates.

We examined data for 27 948 women who died of breast-cancer aged 55–74 years between 1980 and 1999 (30 560 cases until 2001). We grouped individuals into 93 clusters, depending on where they lived, and analysed data by use of national population statistics. We analysed time trends in breast-cancer mortality, adjusting for gradual implementations at municipality level, taking as year 0 the month and year in which screening began in a particular municipality. We used a Poisson regression model to estimate the time at which the trend started to turn. We assessed indirectly whether this turning point was related to initiation of screening or adjuvant systemic therapy in four …