Abstract
Purpose To describe screening outcomes from BreastScreen Norway stratified by volumetric breast density (VBD). Materials and Methods This retrospective study included data from 107 949 women aged 50-69 years (mean age ± standard deviation, 58.7 years ± 5.6) who underwent 307 015 screening examinations from 2007 to 2015. Automated software classified mammographic density as nondense (VBD <7.5%) or dense (VBD ≥7.5%). Rates and distributions of screening outcomes (recall, biopsy, screen-detected and interval breast cancer, positive predictive values of recall and of needle biopsy, sensitivity, specificity, and histopathologic tumor characteristics) were analyzed and stratified by density. Tests of proportions, including propensity score and t tests, were used. Results In 28% (87 021 of 307 015) of the screening examinations, the breasts were classified as dense. Recall rates for women with nondense versus dense breasts were 2.7% (5882 of 219 994) and 3.6% (3101 of 87 021); biopsy rates were 1.1% (2359 of 219 994) and 1.4% (1209 of 87 021); rates of screen-detected cancer were 5.5 (1210 of 219 994) and 6.7 (581 of 87 021) per 1000 examinations; and rates of interval breast cancer were 1.2 (199 of 165 324) and 2.8 (185 of 66 674) per 1000 examinations, respectively (P < .001 for all). Sensitivity was 82% (884 of 1083) for nondense breasts and 71% (449 of 634) for dense breasts, whereas specificity was 98% (160 973 of 164 440) and 97% (64 250 of 66 225), respectively (P < .001 for both). For screen-detected cancers, mean tumor diameter was 15.1 mm and 16.6 mm (P = .01), and lymph node-positive disease was found in 18% (170 of 936) and 24% (98 of 417) (P = .02) of women with nondense and dense breasts, respectively. Conclusion Screening examinations of women with dense breasts classified by using automated software resulted in higher recall rate, lower sensitivity, larger tumor diameter, and more lymph node-positive disease compared with women with nondense breasts.
Highlights
Ur study was approved by the data protection official for research at Oslo University Hospital (Oslo, Norway) and the regional committee for medical and health research ethics
volumetric breast density (VBD) measurements ranged from 1% to 52%; 72% (219 994 of 307 015) of examinations were classified as nondense and 28% (87 021 of 307 015) as dense (Table 1, Fig 1)
A lower rate of breast cancer was observed for nondense versus dense breasts: 5.5 (1210 of 219 994) versus 6.7 per 1000 examinations (581 of 87 021) for screen-detected breast cancer, and 1.2 (199 of 165 324) versus 2.8 (185 of 66 674) per 1000 examinations for interval breast cancer, respectively (P, .001 for both)
Summary
We aimed to determine the rates of recall and biopsy, rates of cancer detection, positive predictive values, sensitivity, specificity, histopathologic tumor characteristics, odds of breast cancer, and predicted numbers of breast cancer cases based on volumetric breast density (VBD) categories
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