Quantification of masking risk in screening mammography with volumetric breast density maps.
Fibroglandular tissue may mask breast cancers, thereby reducing the sensitivity of mammography. Here, we investigate methods for identification of women at high risk of a masked tumor, who could benefit from additional imaging.



The last negative screening mammograms of 111 women with interval cancer (IC) within 12 months after the examination and 1110 selected normal screening exams from women without cancer were used. From the mammograms, volumetric breast density maps were computed, which provide the dense tissue thickness for each pixel location. With these maps, three measurements were derived: (1) percent dense volume (PDV), (2) percent area where dense tissue thickness exceeds 1 cm (PDA), and (3) dense tissue masking model (DTMM). Breast density was scored by a breast radiologist using BI-RADS. Women with heterogeneously and extremely dense breasts were considered at high masking risk. For each masking measure, mammograms were divided into a high- and low-risk category such that the same proportion of the controls is at high masking risk as with BI-RADS.



Of the women with IC, 66.1, 71.9, 69.2, and 63.0% were categorized to be at high masking risk with PDV, PDA, DTMM, and BI-RADS, respectively, against 38.5% of the controls. The proportion of IC at high masking risk is statistically significantly different between BI-RADS and PDA (p-value 0.022). Differences between BI-RADS and PDV, or BI-RADS and DTMM, are not statistically significant.



Measures based on density maps, and in particular PDA, are promising tools to identify women at high risk for a masked cancer.
Department of Radiology and Nuclear Medicine, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands. Katharina.Holland@radboudumc.nl.
Katharina
K
Holland
Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, PO Box 85500, 3508 GA, Utrecht, The Netherlands.
Carla H
CH
van Gils
Department of Radiology and Nuclear Medicine, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.
Ritse M
RM
Mann
Department of Radiology and Nuclear Medicine, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.
Nico
N
Karssemeijer
D000368:Aged; D016477:Artifacts; D000071060:Breast Density; D001943:Breast Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology*; D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods; D008403:Mass Screening; D008875:Middle Aged; D009426:Netherlands; D010470:Perceptual Masking; D012372:ROC Curve
Breast cancer screening; Masking; Risk stratification; Supplemental screening; Volumetric breast density