[Nationwide breast cancer screening fully accomplished; results from the implementation phase 1990-1997. National Evaluation Team for Breast Cancer Screening].

OBJECTIVE

To present an overview of the main results of the nationwide breast cancer screening programme implemented in the Netherlands from 1990 to 1997 and providing a biennial mammography for all women aged 50-69 years.

METHOD

Data on screening examinations were provided by the 9 regional screening organisations; data on interval cancers and on breast cancers in unscreened women were provided by the regional cancer registries after linkage of registry data with data on screened women. The results observed were compared with the expectations used in the cost effectiveness analysis before the start of the population screening.

RESULTS

Of almost 4 million women invited, 78.5% attended for screening. The screening resulted in 13.1 referrals, 9.2 biopsies and 6.1 breast cancers detected per 1,000 initially screened women, and in 6.9 referrals, 4.5 biopsies and 3.5 detected breast cancers per 1,000 subsequently screened women. All these parameters showed a clear variation at regional level. In the first 2 years after initial screens 0.96 interval cancers per 1,000 women-years were diagnosed (0.93 per 1,000 women-years after subsequent screens). Of all screen-detected cancers 76% were ductal carcinomas in situ (13%) or invasive cancers < or = 20 mm in size (63%); 26% of the invasive cancers were lymph node positive. This stage distribution was clearly more favourable than that of interval cancers and of the breast cancers diagnosed in unscreened women. The detection of breast cancer at subsequent screening was lower than expected and the staging of the carcinomas was less favourable than expected; the other results were largely in accordance with the expectations.