Difference in Background Parenchymal Enhancement on Contrast-Enhanced Mammography in Treatment-Naïve Versus Systemic Neoadjuvant Chemotherapy Patients.

Background and purpose Contrast-enhanced mammography (CEM) has emerged as a valuable imaging modality for breast cancer detection and management. Background parenchymal enhancement (BPE) reflects the level of normal glandular tissue enhancement and can vary based on physiological and pathological factors. Understanding the patterns of BPE in different patient populations, including post-treatment women, may provide insights into breast tissue response to therapy and aid in optimizing imaging interpretation. The purpose is to evaluate whether there is a difference in BPE on CEM in women who have undergone systemic neoadjuvant chemotherapy (NAC) to the breast compared with treatment-naïve women. Methods Retrospective single-center cohort study of consecutive women who underwent CEM from December 2019 to December 2024 inclusive. The degree of BPE, as defined by the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) Atlas for each examination, was independently reviewed by two specialized breast radiologists, and interobserver agreement was evaluated using the kappa statistic (kappa score = 1.0 for both treatment-naïve and post-NAC groups) and categorized into minimal, mild, moderate, or marked. Treatment status was recorded. Cases that did not have paired data were excluded. SPSS version 29.0.0.0 (IBM SPSS Statistics for Windows, IBM Corp., Armonk, NY) was used for analysis. Results Among 132 studies, 45 cases had paired data. The background BPE showed no statistical difference between treatment-naïve and post-NAC groups. Treatment-naïve patients predominantly showed minimal or mild BPE (46.7% and 31.1%, respectively), and lower percentages of moderate to marked BPE (20% and 2.2%, respectively). Post-NAC patients demonstrated no statistically significant difference in BPE categories, with 42.2% showing minimal and 55.6% mild BPE. Moderate or marked BPE was infrequent (2.2% and 0%, respectively). Conclusions No statistically significant difference in BPE between treatment-naïve and post-NAC groups (p = 0.084).