Differences in longitudinal changes of mammographic breast percent density among normal, benign, and cancer patients: a preliminary study

This study investigated the potential of longitudinal mammographic breast percent density (PD) to differentiate high-risk, benign, and normal/healthy women for developing breast cancer. We used a dataset of sequential screening mammography exams of 406 women from the University of Pittsburgh Medical Cancer. Each subject had four sequential mammograms where the first three exams were cancer negative and the last had either a biopsy proven cancer (N = 116), benign lesions (rated as BI-RADS 2) (N = 70), or normal results, rated as BI-RADS 1(N = 220). We computed the PD, the ratio of dense tissue over the breast area, using our in-house breast density segmentation algorithm for four standard views of each exam. We then averaged the PD from all four views to produce an exam PD for a given subject at a given screening time point. Then, we fitted a linear curve on the PD values from three priors and extracted the slope as a measure of relative breast density changes over time. We compared the slope values of each group (cancer, benign, and normal) using a two-sample student's t-test. We found that the slopes of all groups were negative (group medians ranged from – 0.0102 to – 0.006), meaning the breast density decreased over time. However, their rates were different. The slope values of the benign and normal groups were similar to each other (p = 0.442), but they were much faster than that of the cancer group (p < 0.032).