Pain-preventing strategies in mammography: an observational study of simultaneously recorded pain and breast mechanics throughout the entire breast compression cycle

Abstract

Background: Many women consider mammography painful. Existing studies on pain-preventing strategies only mention pain scores reported before and after breast compression. Studying the pain dynamics during the entire compression cycle may provide new insights for effective pain-preventing strategies.

Methods: This observational study included 117 women who consented to use a custom turning knob to indicate their pain experience during standard mammographic breast compressions in the Academic Medical Center in Amsterdam, The Netherlands. The breast thickness, compression force, contact area, contact pressure and pain experience were recorded continuously. Breast volume was calculated retrospectively from the mammograms. We visualized the progression of pain in relation to breast mechanics for five groups of breast volumes and we performed multivariable regressions to identify factors that significantly predict pain experience.

Results: Breast compressions consisted of a deformation phase for flattening, and a clamping phase for immobilization. The clamping phase lasted 12.8 ± 3.6 seconds (average ± standard deviation), 1.7 times longer than the 7.5 ± 2.6 seconds deformation phase. During the clamping phase, the average pain score increased from 4.75 to 5.88 (+24 %) on a 0 - 10 Numerical Rating Scale (NRS), and the proportion of women who reached severe pain (NRS ≥ 7) increased from 23 % to 50 % (more than doubled). Moderate pain (NRS ≥ 4) was reported up to four days after the mammogram. Multivariable analysis showed that pain recollection of the previous mammogram and breast pain before the compression, are significant predictors for pain. Women with smallest breasts experienced most pain: They received highest contact pressures (force divided by contact area) and the pressure increased at the highest rate.

Conclusion: We suggest further research on two pain-preventing strategies: 1) using a personalized compression protocol by applying to all breasts the same target pressure at the same, slow rate, and 2) shortening the phase during which the breast is clamped.

Figure 1

Custom turning knob used for recording time-varying pain throughout the entire breast compression cycle.

Figure 2

Selected examples of raw data recordings for five breast volumes: Actual-time progression of the recorded variables and the dynamic pain score. The gray vertical dashed lines indicate the deformation and clamping phase. For reference: the gray horizontal bar in the middle-right panel indicates the range of normal blood pressures.

Figure 3

Mean ± 95% confidence interval for all 324 compressions stratified by breast volume into five equally sized groups: Progression of the recorded variables and the dynamic pain scores on a relative time scale. Boxplots represent the distributions of values at the end of compression as well as (bottom right) for recollected pain scores of the previous mammogram and for pain scores five days after the mammogram. Boxes are mean ± one standard deviation and whiskers extend until the furthest outlier with a maximum of one standard deviation. For reference: the gray horizontal bar in the middle-right panel indicates the range of normal blood pressures.

Figure 4

Breast deformation curves for five selected example compressions. The curves are obtained by plotting the Th(t)-values from the deformation phase as function of the corresponding and simultaneously recorded F(t)-values.