Women with dense breast tissue have a higher rate of recall, higher rates of screen-detected and interval breast cancer, and more lymph node-positive disease revealed mammographic screening of breasts using automated software.
The study, published in the journal Radiology supports automated measurements as a future standard to ensure objective breast density classification for breast cancer screening.
Solveig Hofvind, Cancer Registry of Norway, Oslo, and colleagues conducted the study to describe screening outcomes from BreastScreen Norway stratified by volumetric breast density (VBD).
Previous studies have shown that women with mammographically dense breasts face a higher risk of breast cancer and missed cancers than those with non-dense breasts, partly because the superimposition of dense breast tissue on mammograms leads to a masking effect, causing some cancers to go undetected. However, the majority of those studies relied on subjective density assessments.
For the new study, the investigators used automated software to help classify mammographic density in 107,949 women ages 50 to 69 from BreastScreen Norway, a national program that offers women screening every two years. The researchers looked at a total of 307,015 digital screening examinations that took place from 2007 to 2015.
This retrospective study included data from 107 949 women aged 50–69 years (mean age ± standard deviation, 58.7 years ± 5.6). 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.
- 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.
- 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.
- 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.
“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,” concluded the authors.
For further reference log on to https://doi.org/10.1148/radiol.2018172972