Contrast-enhanced mammography (CEM) supplies two complementary views of the breast: mammographic density (MD), which reflects anatomical features, and background parenchymal enhancement (BPE), which reflects vascular uptake. In routine screening, both are reported, yet they do not behave in the same way over time. An evaluation of consecutive negative annual examinations across younger and older women shows that BPE changes more between visits than MD, including shifts across broad categories. The pattern appears in both age groups, indicating that greater movement in BPE is not confined to those of reproductive age. These observations are directly relevant to day-to-day interpretation, appointment scheduling and the way longitudinal change is described in screening reports, as services look to balance consistency with practical workflows.
Different Signals, Different Stability
Across repeated screening visits, MD tended to remain steady for most women, while BPE moved more often and sometimes more than a single step on the reporting scale. The contrast highlights a key difference between what the two measures capture. MD, rooted in anatomy, is relatively stable across the years. BPE, which reflects enhancement after contrast administration, behaves more like a dynamic signal that can vary from one examination to the next. Importantly, the greater variability in BPE was seen in both younger and older cohorts. A woman with low BPE at one visit later had high BPE at a subsequent visit, showing that change can occur in either direction over time. For clinicians reading consecutive annual screens, the practical point is clear: variation in BPE is common even when overall screening circumstances remain similar, whereas density readings are much less likely to change markedly from year to year.
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The finding that BPE fluctuates more than MD also matters for how longitudinal comparisons are framed. When a measure is known to move between categories without other changes in care, readers and referrers may need to place more emphasis on overall imaging context rather than a single threshold crossing. By contrast, because MD tends to remain stable, a change in density classification carries different weight and may warrant separate consideration. Recognising these distinct behaviours can help align expectations across disciplines and support clearer communication of what constitutes meaningful change over time.
Scheduling and Reporting in Routine Practice
Local appointment policies did not align CEM examinations with any particular point in the menstrual cycle, and menopausal status was not uniformly recorded in the screening pathway. Despite this lack of cycle-based scheduling, BPE varied in both younger and older women. The observation suggests that strict targeting of a specific phase may be less critical for CEM workflows than sometimes assumed. Because fluctuations occurred even in women beyond the reproductive transition, cycle timing alone cannot fully account for the pattern seen in BPE.
These dynamics have reporting consequences. Where screening programmes compare images over several years, reports that describe movement in BPE should reflect the known propensity of this measure to shift between categories. Overinterpretation of single-visit changes risks obscuring the broader trajectory within a series. Clear language that distinguishes the relative stability of MD from the more labile behaviour of BPE can help referrers and patients understand why year-to-year variation in enhancement may not carry the same implications as a genuine change in density. In practical terms, the experience of comparable variability across age groups, together with non–cycle-aligned scheduling, supports a pragmatic approach to appointments focused on service efficiency and image quality rather than rigid timing rules.
Acquisition, Reading and Standardisation
CEM introduces practical factors that can influence how BPE is categorised from one examination to the next. Image capture is sequential rather than simultaneous, which can introduce minor timing differences within an examination or across years. Compression is applied after contrast administration and, as in other breast imaging contexts, compression technique can vary between radiographers. These procedural nuances may contribute to changes in how vascular uptake appears on the resulting images.
Reader-related factors are also relevant. Agreement for BPE is generally good, yet variation persists, and routine clinical reading may be influenced by prior reports when comparisons are made over time. Such real-world conditions, while reflective of everyday practice, can introduce subtle shifts in categorisation that accumulate across a series of examinations. Unlike breast MRI, where automated volumetric approaches and artificial intelligence methods are advancing quantification of enhancement, there are not yet widely established quantitative tools for BPE assessment in CEM. This leaves most services reliant on categorical visual grading, which is inherently more susceptible to variation than standardised numeric outputs.
Together, these acquisition and interpretation elements point to the value of greater standardisation. Consistent protocols for timing, compression and post-contrast workflow, coupled with harmonised approaches to assessment, could help reduce variability and strengthen reproducibility. As technological solutions mature, quantitative or semi-quantitative methods tailored to CEM may further support stable longitudinal comparisons, offering readers more consistent anchors when judging change within a patient’s screening history.
BPE on CEM is more changeable over time than MD across both younger and older screening populations. This consistent pattern cautions against treating BPE as a fixed individual marker when making longitudinal judgements and supports pragmatic scheduling that does not depend on strict cycle timing. Clear reporting that differentiates the relative stability of density from the dynamic nature of enhancement can improve the usefulness of year-to-year comparisons. Progress toward more standardised acquisition and assessment, and the development of suitable quantitative tools for CEM, would help reduce variability and enhance the interpretability of BPE in routine screening practice.
Source: European Journal of Radiology
Image Credit: iStock
