Asymmetric Complementarity: A Subtype-Specific Strategy via Visual Assessment of DCE-MRI and DWI for Evaluating NAT Efficacy in Breast Cancer.

Rationale

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Objectives

To evaluate dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted imaging (DWI), based on clinical visual assessment for predicting pathological complete response (pCR) and measuring residual tumor size after neoadjuvant therapy (NAT) across breast cancer subtypes.

Materials And Methods

This retrospective study included 248 patients. Two radiologists, blinded to pathological results, visually assessed DCE-MRI and DWI (including ADC maps) for radiological complete response (rCR) and measured residual tumor size. Diagnostic performance (vs. pCR) and size agreement (intraclass correlation coefficient, ICC) were compared between sequences and across three molecular subtypes: HR+/HER2-, HER2+, and triple-negative breast cancer (TNBC). Bonferroni correction was applied.

Results

DCE-MRI showed higher specificity, positive predictive value (PPV), and accuracy, DWI showed higher sensitivity (all P < 0.05). Subtype analysis: HER2+ exhibited a trend toward symmetric complementarity (DWI-high NPV, DCE-MRI-high PPV; sensitivity difference not significant after correction, adjusted P = 0.066); HR+/HER2- showed DCE-MRI dominance (DWI very low PPV/specificity); TNBC showed no significant differences(n = 30, preliminary). Interobserver κ: 0.77 (DCE-MRI), 0.85 (DWI). Interobserver ICC for size:0.96 (both). DCE-MRI demonstrated superior size concordance with pathology (ICC: 0.91 vs. 0.51, P < 0.001).

Conclusion

DCE-MRI and DWI exhibit subtype-dependent asymmetric complementarity. For HER2+, both are complementary (DWI high NPV, DCE-MRI high PPV). For HR+/HER2-, DCE-MRI is the primary anchor (DWI limited). For TNBC, findings are preliminary (larger studies needed). DCE-MRI is more reliable for size measurement. This framework provides a molecular subtype-specific visual interpretation guide for clinical practice.