Pathologic complete response and residual disease after neoadjuvant chemotherapy in breast cancer: Comparison of contrast-enhanced mammography, DCE-MRI, and ¹⁸F-FDG PET/CT.

Accurate assessment of breast cancer response to neoadjuvant chemotherapy (NAC) is important for surgical planning. We compared contrast-enhanced mammography (CEM), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for predicting breast pathologic complete response (pCR) and assessing residual disease. This retrospective single-center study included 76 patients who underwent all three modalities before and after NAC, followed by surgery. Postoperative histopathology was the reference standard; breast pCR was defined as the absence of residual invasive carcinoma in the breast, irrespective of residual ductal carcinoma in situ. Breast pCR occurred in 28 patients (36.8%). CEM had higher sensitivity than DCE-MRI (89.3% versus 60.7%; p = 0.012) and the highest negative predictive value (92.1%), whereas DCE-MRI had the highest specificity (85.4%) and positive predictive value (70.8%). Accuracy was 79.0%, 76.3%, and 73.7% for CEM, DCE-MRI, and ¹⁸F-FDG PET/CT, respectively, without a significant difference among modalities (p = 0.661). Corresponding areas under the receiver operating characteristic curve were 0.841, 0.844, and 0.769. Among 48 patients with residual invasive disease, intraclass correlation coefficients for CEM and DCE-MRI measurements versus pathology were 0.733 and 0.773, respectively. However, 95% limits of agreement were wide (-34.16 to 25.16 mm and -29.26 to 20.93 mm, respectively), indicating substantial individual-level discrepancies. CEM showed promise for post-NAC breast response assessment in this selected cohort, but the findings do not establish equivalence or interchangeability with DCE-MRI. Individual tumor size estimates require caution, and prospective multicenter validation is warranted.