Jacky Luiten

8 | Chapter 1 Introduction In 1968 the principles of screening for diseases were defined by the World Health Organization. 1 The aim of screening is to detect and subsequently treat disease in an early stage to decrease related morbidity and mortality. 2,3 In 1971 the Health Insurance Plan of New York published the first randomized trial of breast cancer screening, which compared mammography and clinical breast examination. 4 The favorable outcome of this trial and subsequent studies, together with the results of cost‐benefit analysis led to the start of the first population‐based breast cancer screening program in the UK in 1988. 5 In the Netherlands a mammography screening program was gradually implemented between 1989 and 1996 by the National Institute for Public Health and Environment (RIVM, Rijksinstituut voor Volksgezondheid en Milieu ). This nation‐wide program involves a free of charge biennial screening mammography for women aged 50‐70 years. In 1998‐1999, the upper age limit was extended from 70 to 75 years. 6,7 Yearly, approximately 1.3 million women are invited to the screening program, of whom almost 1 million participate. Ever since the introduction of the screening program the attendance rate is approximately 80%. 8 In recent years the recall rate was around 23 per 1000 screens, with a cancer detection rate of 6.8 per 1000 screens. 8 Mammography was originally carried out using general‐purpose X‐ray imaging systems. In the late 1970s screen‐film mammography (SFM) was introduced, resulting in high spatial resolution allowing better discrimination of fine microcalcifications and morphological features of soft tissue structures, such as masses. 9 The introduction of full field digital mammography (FFDM) around 2000 provided a marked improvement in imaging, especially of dense breasts, resulting in a higher specificity and sensitivity for small lesions. 10 In the Netherlands the introduction of FFDM at screening was completed in 2010. 11‐14 Recently, for women with extremely dense breast tissue and normal results on mammography the added value of a supplemental MRI screening was tested in a randomized clinical trial. The MRI resulted in an increased cancer detection rate resulting in the diagnosis of significantly fewer interval cancers, but also led to an increased false positive rate. 15 To this end, the use of MRI is still debated and longer follow‐up is needed to assess the effect on advanced cancers and mortality. The principal benefit of screening is the early detection of breast cancer leading to fewer advanced stage cancers, a lower breast cancer mortality rate and less morbidity. 16‐18