Mammographic compression pressure as a predictor of interval cancer

Purpose: To identify mammographic image quality indicators (IQI) predictive of interval breast cancers (IC) as opposed to screen-detected cancers (SDC). Methods: Eligible cases for the study were raw, routine recall, screening exams acquired at two UK sites between 2010- 2018, from the OPTIMAM database. Women were matched 3:1 (SDC, n=965 versus IC, n=326), by age (nearest), screening site, breast density grade, Xray system vendor, and compression paddle. Images of the affected breast for prior (IC only) or incident (SDC only) exams were processed using automated software to obtain volumetric breast density (VBD) and IQI metrics related to compression and breast positioning. Compression pressure (CP) was categorised into tertiles or low/target/high (<7/7-15/<15 kPa) groups. Univariate and logistic regression analyses were used to identify significant predictors of IC versus SDC. Results: Compared to SDC, IC had lower median CP (7.9 versus 8.6 kPa, p<0.05). Multivariate analysis found only CP to be significantly associated with the risk of IC versus SDC, with odds ratios (OR) and 95% confidence intervals of 0.93 (0.89-0.97) per unit CP. Compared to low CP, target CP was significantly associated with a lower IC versus SDC risk at the breast level [OR=0.73 (0.56-0.95)] and for mediolateral oblique views [OR=0.77 (0.59-0.99)]. Comparing the third and first tertile, CP was significantly associated with lower risk of IC versus SDC [0.64 (0.47-0.87)], with very similar results when analysed per view. Conclusions: CP was found to be a significant predictor of IC versus SDC, with higher CP being associated with a lower risk of IC.