Jacky Luiten

116 | Chapter 8 Summary In the Netherlands a nation ‐ wide biennial mammographic screening program for women aged 50 ‐ 70 years was set up between 1989 and 1996. In 1998 ‐ 1999, the upper age limit of the program was extended from 70 to 75 years and in 2009 ‐ 2010 screen film mammography (SFM) was replaced by full field digital mammography (FFDM). The impact of the transition to digital mammography was analyzed in chapter 2 . The transition was characterized by an increase of the overall detection rate of ductal carcinoma in situ (DCIS) from 0.8 per 1000 to 1.6 per 1000 screens ( p =<0.001), as well as an increase of the detection rate of invasive cancers from 4.1 per 1000 to 5.1 per 1000 screens ( p =0.003). The majority of the DCIS lesions detected by screening mammography was high grade (48.2%), whereas the majority of the invasive breast cancer was low grade (45.4%) or intermediate grade (41.6%). The grade distribution the years after the transition to FFDM remained stable when compared to the era of SFM screening. It is hypothesized that if high grade DCIS develops towards invasive carcinoma, it is more likely that it will become a high grade rather than a low or intermediate grade carcinoma. 1,2 Our findings therefore suggest that screening reduces the incidence of high grade invasive carcinoma through early diagnosis and treatment of high grade DCIS. During the transition from SFM to FFDM the cancer detection rate remained stable, while the absolute number of screening examinations gradually increased from 66,750 in the last SFM period to 131,224 in the first FFDM period. In those same periods, the recall rate increased from 1.3% to 3.3%. All recalled women require additional radiologic examinations which may be followed by percutaneous or surgical biopsy in order to obtain a definitive pathology result. Chapter 3 evaluates the use and value of surgical excision biopsies for diagnostic purposes over the last two decades in women undergoing mammographic screening. All recalled women who underwent an excision biopsy from January 1997 to January 2017 were analyzed. It has been postulated that, with the introduction and widespread use of (stereotactic) core needle biopsy ((S)CNB), a surgical excision biopsy would become an obsolete procedure. 3,4 Therefore, a distinction was made between primary excision biopsies (performed as first diagnostic intervention) and secondary excision biopsies (performed secondary to pathologic findings at percutaneous CNB). Indeed, the use of primary excision biopsies decreased from 4.3 per 1000 screens in 1997 ‐ 1998 to 0 per 1000 screens