Optimizing abbreviated breast MRI protocols for the early assessment of neoadjuvant chemotherapy response in breast cancer

Background: The widespread use of breast magnetic resonance imaging (MRI) for monitoring tumor response to neoadjuvant chemotherapy (NAC) is restricted by its limited accessibility and substantial interpretive workload. This study aimed to evaluate various abbreviated breast MRI protocols and identify the optimal approach for the early assessment of NAC response in breast cancer patients. Methods: A total of 359 patients with invasive breast cancer from three centers, who underwent full-protocol breast MRI at baseline and after two cycles of NAC, were retrospectively included in the study [primary cohort, n=169; external validation cohorts (EVCs), n=89 and 101]. Six abbreviated protocols were reconstructed from the full protocol, each comprising T2-weighted imaging plus a single dynamic contrast-enhanced (DCE) phase acquired at approximately 20, 90, or 270 s after injection; diffusion-weighted imaging (DWI) was also included in Protocols 4-6. Percentage changes in tumor size, the tumor-to-parenchyma signal enhancement ratio (SER), and the apparent diffusion coefficient (ADC) between MRI at the baseline and after two cycles of NAC (Δ%Size, Δ%SER, and Δ%ADC) were calculated. Diagnostic performance was assessed using receiver operating characteristic (ROC) analysis with the area under the curve (AUC), and compared using the DeLong test. Scan acquisition and interpretation times were also recorded to assess efficiency. Results: P6, P