While firm breast compression is generally thought to be required for high quality mammograms the relationship between the amount of compression and screening performance has not been studied systematically. The aim of this study is to determine breast cancer screening outcomes in relation to the compression pressure applied during mammography.METHOD AND MATERIALS
A consecutive series of 111,870 digital screening examinations performed in 53,684 women between July 2003 and December 2011 was collected from a screening centre operating within a nationwide breast cancer screening program. A total of 662 screen-detected cancers were included in this series, while 280 interval cancers corresponding to the selected exams were identified by linkage to the Dutch Cancer Registry. Using a research version of Volpara Density software (Volpara Solutions, Wellington, NZ) breast volume (V), dense tissue volume (VD), and volumetric density grade (VDG), were estimated for each exam, while compression pressure was estimated for medio-lateral oblique (MLO) view by dividing the compression force by the area of contact surface between the breast and the compression paddle. We calculated frequencies of recalls, screen-detected cancers, and interval cancers stratified by compression pressure in five groups and derived program sensitivity, specificity, and positive predictive value (PPV). In addition, for each group we computed mean values of V, VD, and VDG. For statistical analysis Pearson's Chi-squared test was used.RESULTS
Screening outcomes were different in the five compression pressure groups (p=0.004). Program sensitivity decreased with increasing pressure (77.0%, 69.7%, 74.5%, 63.2%, 66.7%) (p=0.02), specificity was similar, and PPV was highest in the midrange of pressure (28.5%, 31.0%, 34.2%, 26.7%, 25.7%) (p=0.03). Cutoff points for pressure dividing the data in groups of 20% were 7.7, 9.2, 10.7, 12.8 kPa. V and VD both decreased with increasing pressure. Mean VDG moderately increased (1.75, 2.0, 2.2, 2.4, 2.8).CONCLUSION
Results suggest that if too much pressure is applied during mammography this may increase interval cancer rates and decrease PPV.CLINICAL RELEVANCE/APPLICATION
Controlling pressure during mammography is important to decrease the discomfort experienced by women, but it may also be required to optimize screening outcomes.