Elsevier

The Lancet

Volume 361, Issue 9367, 26 April 2003, Pages 1411-1417
The Lancet

Articles
Initiation of population-based mammography screening in Dutch municipalities and effect on breast-cancer mortality: a systematic review

https://doi.org/10.1016/S0140-6736(03)13132-7Get rights and content

Summary

Background

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.

Methods

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 clusters defined according to when screening was implemented.

Findings

Compared with rates in 1986–88, breast-cancer mortality rates in women aged 55–74 years fell significantly in 1997 and subsequent years as predicted, reaching −19·9% in 2001. Mortality rates had been increasing by an annual 0·3% until screening was introduced; thereafter we noted a decline of 1·7% per year (95% CI 2·39–0·96) in women aged 55–74 years and of 1·2% in those aged 45–54 (2·40 to 0·07). The turning point in mortality trends arose at around year 0. Adjuvant systemic therapy is unlikely to be the cause of this turning point, since the mortality rates continued to rise up to 1 year after implementation in municipalities where screening began after 1995.

Interpretation

Routine mammography screening can reduce breast-cancer mortality rates in women aged 55–74 years.

Introduction

In randomised controlled trials, mammography screening has been shown to reduce breast-cancer mortality rates in women aged 50–69 years.1 In view of this finding, several countries introduced population-based screening in the late 1980s and early 1990s. However, although the results of an assessment2 of four Swedish trials showed that the beneficial effect in terms of breast-cancer mortality continued long after the trials had ended,2 the effect observed in trials is no guarantee for the effectiveness of population-based screening programmes. Such programmes should be assessed at an individual level, taking into account the screening behaviour of each woman, the cases diagnosed before the start of a programme, and whether a woman has received an invitation to screening.

Whether national population statistics3, 4, 5, 6 or some level of individual data7, 8 is used, findings of assessments have indicated that breast-cancer mortality is falling in the target age-groups for screening in Sweden,4, 8 Finland,7 England and Wales,3, 6 and the Netherlands.5 Such analyses must, however, allow for the effect of changes and improvements in treatment and other (risk) factors that might affect mortality. Indeed, the lack of availability and accessibility to the data needed make assessment of the efficacy of screening on an individual level is difficult in many countries.

In the Netherlands, the nationwide mammography screening programme for women aged 50–69 years was gradually implemented between 1989 and 1997. By 1997, women of the target age-group in all municipalities were receiving invitations for screening once every other year, and results of early outcome assessments9, 10 indicate that the programme is having a positive effect. Our aim was to assess the effects of the screening programme on breast-cancer mortality rates in the Netherlands between 1980 and 2001.

Section snippets

Methods

The nationwide mammography screening programme for women aged 50–69 years was launched in 1988–89 in municipalities adjacent to Utrecht and Nijmegen, the two municipalities in the Netherlands in which the programme had been piloted. Between 1990 and 1997, the programme was extended to all other regions. During the study period (1980 to 1999), municipal borders were redrawn at various times—causing the number of municipalities to fall from 812 in 1980 to 672 in 1990 and 538 in 1999—and names of

Results

Table 1 shows the breast-cancer mortality rates in the Netherlands for the years 1986–88 to 2001 in women aged 55–74 years. Compared with 1986–88 mortality rates started to fall between 1991 and 1996, a decrease that became significant in 1997 and remained so in subsequent years.

Figure 1 shows the age-standardised breast-cancer mortality rates observed in 1986–2001 and those predicted by MISCAN in situations with and without screening, for the age-groups 45–54, 55–64, 65–74, and 75–84 years.

Discussion

Our findings show that screening with mammography contributes to the reduction in breast-cancer mortality rates seen in the Netherlands.

Several studies have described a positive relation between breast-cancer mortality and the introduction of mammography screening at national or regional level.6, 7, 8, 15, 16, 17, 18, 19 Generally, these studies report reduced breast-cancer mortality rates that vary between 6% and 63%, with the largest reductions noted in studies analysing the refined

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