Contrast-Enhanced Mammography vs. Breast MRI for Assessing Neoadjuvant Chemotherapy Response: A Prospective Clinical Comparison Study

<b>Objective</b>: To compare contrast-enhanced mammography (CEM) with breast magnetic resonance imaging (MRI) in evaluating residual tumor size and pathological complete response after neoadjuvant chemotherapy (NAC) in breast cancer patients. <b>Methods</b>: This prospective study included patients with histopathologically confirmed breast cancer who were scheduled to receive NAC followed by surgery. All patients underwent both CEM and breast MRI before initiation of NAC and within seven days after completion of treatment. Surgery was performed at a median of 14 days after post-treatment imaging. Residual tumor size measurements obtained by both imaging modalities were compared with histopathological findings, which served as the reference standard. Pathological complete response was defined as the absence of residual invasive carcinoma in the surgical specimen. <b>Results</b>: A total of 74 female patients were included. CEM estimated residual tumor size within ±1 cm of histopathology in 84.7% of cases, whereas MRI achieved this accuracy in 76.4%. Agreement with histopathology was higher for CEM than for MRI. In predicting pathological complete response, CEM demonstrated higher sensitivity (91.3%) and negative predictive value compared with MRI; however, this difference did not reach statistical significance (<i>p</i> = 0.24). MRI showed slightly higher specificity. Pathological complete response was observed in 31.1% of patients. <b>Conclusion</b>: Contrast-enhanced mammography demonstrated performance comparable to breast MRI in assessing response to neoadjuvant chemotherapy, with numerically higher sensitivity for predicting pathological complete response. CEM may represent a practical and accessible alternative to MRI, particularly in settings where MRI is unavailable or contraindicated. These findings support the clinical use of CEM as a reliable alternative imaging modality for response assessment.