Jacky Luiten

Trends in incidence and tumor grade in screen‐detected DCIS and invasive breast cancer | 21 2 DCIS DCIS was diagnosed in 623 patients out of 3059 true positive recalls (20.4%, Table 2.2). The majority of the DCIS lesions (80.7%) presented as suspicious microcalcifications at screening mammography. Almost half of the screen‐detected cases of DCIS were high grade lesions (48.2%; 300 women) Table 2.2 Characteristics of DCIS and invasive breast cancers detected at bi‐annual screening mammography. True positive recall (%) 623 (20.4) 2436 (79.6) <0.001* Initial screens (%) 113 (18.1) 284 (11.7) Subsequent screens (%) 510 (81.9) 2152 (88.3) Positive predictive value of recall (%) 4.8 18.8 Cancer detection rate per 1000 screens 1.3 5.0 Screening method 0.039* Screen–film mammography (%) 126 (20.2) 588 (24.1) Full–field digital mammography (%) 497 (79.8) 1848 (75.9) Mammographic abnormalities (%) <0.001* Suspicious mass 52 (8.3) 1736 (71.3) Suspicious microcalcifications 503 (80.7) 229 (9.4) Suspicious mass with microcalcifications 63 (10.1) 244 (10.0) Asymmetry 2 (0.3) 37 (1.5) Architectural distortion 3 (0.5) 188 (7.7) Other mammographic abnormality Tumor grade (%) – 2 (0.1) <0.001* Low 124 (19.9) 1106 (45.4) Intermediate 199 (31.9) 1013 (41.6) High 300 (48.2) 275 (11.3) Unknown – 42 (1.7) * χ 2 test. Table 2.3 shows the distribution of histological grade of screen‐detected DCIS. In both SFM‐only cohorts (2005‐2007 vs. 2007‐2009), the proportional distribution of DCIS by histological grade was largely comparable; low grade 12.3% vs. 16.1%, intermediate grade 16.9% vs. 30.4% and high grade 70.8% vs. 53.8% ( p =0.131; Table 2.3). No significant differences were found regarding the DCIS rate per 1000 women screened, analyzed by grade; low grade 0.1 vs. 0.1 per 1000 screens ( p =0.803), intermediate grade 0.2 vs. 0.3 per 1000 screens ( p =0.254) and high grade 0.7 vs. 0.5 per 1000 screens ( p =0.07; Figure 2.1). Similarly, in both FFDM‐only cohorts (2011‐2013 vs. 2013‐2015) the proportions of low, intermediate and high grade DCIS were also comparable; low grade 18.2% versus 15.8%, intermediate grade 33.1% vs. 35.7% and high grade 48.6% vs. 48.8% ( p =0.815). Moreover, when analyzed according to grade, no differences were observed between the rate per 1000 women screened; low grade 0.3 vs. 0.2 per 1000 screens ( p =0.194), intermediate grade 0.5 vs. 0.4 per 1000 screens ( p =0.464) and high grade 0.7 vs. 0.6 per 1000 screens ( p =0.203; Figure 2.1).