Jacky Luiten

Trends in frequency and outcome of high‐risk breast lesions at CNB |51 4 screening organization with respect to final outcome, one of the screening radiologists obtained the reports of the radiologic examinations, the biopsy reports and surgical reports of all recalled women through regular visits at these hospitals. The follow‐up period of the recalled women was two years, which is the period until the next biennial screening round. Only women who gave written informed consent to use their data for quality assurance of the screening program and for scientific purposes were included in this analysis. Our study was performed under the national permit for breast cancer screening, which is issued by the Ministry of Health, Welfare and Sports after advice of the Dutch Health Council and did not require an additional ethical approval. Statistical analysis Trends over time and variations between subgroups were expressed using proportions. The chi‐square test was used to compare proportional differences, or the Fischer’s Exact Test when expected values were too small. Values of p <0.05 were considered statistically significant. Statistical analyses were performed using SPSS, version 24.0 (SPSS, Inc., Chicago, IL). Results Overall screening outcome A total of 376,519 screens (41,204 initial screens and 335,315 subsequent screens) were obtained between January 1, 2011, and December 31, 2016 (Table 4.1). Invasive breast cancer or DCIS was diagnosed in 2,586 of the 11,783 recalled women (recall rate, 3.1%), resulting in 6.9 cancers detected per 1,000 screens and a positive predictive value of recall of 21.9%. Of the 2,586 screen‐detected malignancies, 535 (20.7%) were ductal in situ carcinomas and 2051 (79.3%) were invasive cancers. Trends in frequency and outcome of high‐risk lesions at CNB Of the recalled women 64.8% (7,634/11,783) had been recalled for a suspicious mass and 18.3% (2,162/11,783) for suspicious calcifications (Table 4.2). Over time these percentages varied between 56.4% (2016) and 72.1% (2013) and between 14.0% (2014) and 24.3% (2011), respectively (Table 4.2). A significant increase in the number of asymmetries as mammographic abnormality was observed the last three years of the study period, from 5.2% in 2014 to 12.4% in 2016 ( p <0.001).