Jacky Luiten

16 | Chapter 2 Abstract Purpose In a biennial screening mammography program, we analyzed the trends in incidence of screen‐detected ductal carcinoma in situ (DCIS) and invasive breast cancers in the era of screen‐film mammography (SFM) screening, the period of the transition to full‐field digital mammography (FFDM) screening and the period of FFDM screening. We also investigated a possible association between the incidence and grading of screen‐detected DCIS and invasive breast cancer. Methods In the southern part of the Netherlands, FFDM screening gradually replaced SFM screening between May 2009 and April 2010. We included a consecutive series of 484,422 screens obtained between July 2005 and July 2015 and divided these screens into three groups; SFM‐only cohort, transition cohort and FFDM‐only cohort. Results A total of 3059 recalled women were diagnosed with DCIS ( n =623) or invasive breast cancer ( n =2436). The majority of DCIS were high grade (48.2%), whereas the majority of the invasive breast cancers were low grade (45.4%) or intermediate grade (41.6%). The cancer detection rate (CDR) per 1000 screened women showed the same distribution by grade in both groups. The transition to FFDM was characterized by an increased overall detection rate of invasive cancers. Conclusion Screening mammography detects mostly high grade DCIS and low or intermediate grade invasive cancers. The grade distribution as well as the CDR in the years after the introduction of FFDM remained stable compared to the era of SFM screening. By diagnosing and treating high grade DCIS, which otherwise may develop into high grade invasive carcinoma, our findings provide new evidence for the beneficial value of screening mammography programs.