Predicting Pathologic Complete Response Using Breast MRI After Completion of Neoadjuvant Chemotherapy in Breast Cancer Patients With Residual Calcifications on Mammography.

Background: Determining an appropriate surgical strategy for breast cancer patients with residual suspicious calcifications following neoadjuvant chemotherapy (NAC) remains challenging. Suspicious calcifications often persist on post-treatment mammography, irrespective of tumor viability. This study aimed to identify key predictors of pathologic complete response (pCR) and evaluate the optimal surgical approach for this specific patient cohort.

Methods: A retrospective analysis was conducted on breast cancer patients who presented with residual suspicious calcifications on mammography after NAC but demonstrated a radiologic response on magnetic resonance imaging (MRI), classified as complete (CR) or partial (PR) response. Two radiologists, blinded to pathology results, assessed mammography and MRI findings. Molecular subtypes were classified based on hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status as HR+/HER2-, HR+/HER2+, HR-/HER2+, and triple-negative breast cancer (TNBC). Multivariable regression analysis with an Elastic Net penalty was performed to identify independent predictors of pCR. Diagnostic performance metrics, including sensitivity, specificity, and accuracy, were analyzed by molecular subtypes.

Results: A total of 243 patients, with a mean age of 50.7 years, were included. The overall pCR rate was 33.7%, with HR-/HER2+ demonstrating the highest pCR rate (59.1%) and HR+/HER2- the lowest (3.8%). Multivariable regression analysis identified CR on MRI (compared to PR; odds ratio [OR], 3.13; P = 0.015) and HR-/HER2+ subtype (compared to HR+/HER2-; OR, 29.7; P = 0.005) as significant predictors of pCR. Diagnostic performance metrics of MRI varied by molecular subtype: sensitivity was highest in TNBC (87%) and lowest in HR-/HER2+ (70.4%), while specificity was highest in HR+/HER2- (100%) and lowest in HR-/HER2+ (48.7%). Accuracy was highest in HR+/HER2- (80.8%) and TNBC (78.9%), with lower accuracy in HR+/HER2+ (72.4%) and HR-/HER2+ (57.6%).

Conclusion: Post-treatment MRI response and molecular subtypes are significant predictors of pCR in breast cancer patients with suspicious calcifications after NAC. Nevertheless, complete surgical excision of the calcifications remains advised, particularly for the HR+/HER2- due to the lowest pCR rate and for the HR-/HER2+ due to suboptimal MRI accuracy, despite its highest pCR rate.