*2.3. Imaging Interpretation*

All CESM examinations were carried out two times: just before the beginning of NAC and as a follow-up examination 2 weeks before the end of chemotherapy to evaluate its effect (and to inform decisions about possible changes in therapeutic strategies). For our retrospective analysis, we performed renewed CESM image evaluations with every patient. Such evaluations were made separately by two different radiologists with 20 years of experience and a minimum of 5 years' experience in CESM image interpretation. Radiologists were blinded from each other and from the results of histopathological examination. CESM images were assessed according to the Breast Imaging-Reporting and Data System (BI-RADS) scale. Three measurements were taken in the CC and MLO projections, while the statistical analysis encompassed one—i.e., the largest dimension of the tumor. The tumor dimensions were compared while analyzing:


The response to preoperative chemotherapy was evaluated based on the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria. The response was classified as follows: complete response (CR, disappearance of all lesions); partial response (PR, ≥30% dimensional reduction), stable disease (SD, <30% dimensional reduction/<20% dimensional increase), and progressive disease (PD, ≥20% dimensional increase) [17,32]. For this article, PR, SD, and PD have been classified as "non-CR".

After surgery, a comparison of the NAC response, evaluated with the use of CESM (both low-energy and spectral images), to the histopathological study results was undertaken. Our analysis of histopathology (HP) was used as a "golden standard" against which the effectiveness of both CESM image types in NAC response detection could be analyzed.
