Viscoelastic Mechanical Properties Assessed by Ultrasound Correlates with Tumor Proliferation in Invasive Ductal Breast Cancer: A Preliminary Study.

[OBJECTIVE] Ultrasound-based viscoelastic imaging enables the real-time characterization of tissue properties. In this study, we aimed to investigate the correlation between viscoelastic mechanical properties and tumor proliferation in invasive ductal breast cancer (IDC).

[METHODS] This prospective study consecutively enrolled patients with IDC during October 2024 and January 2025. All patients underwent preoperative shear-wave elastography (SWE) and ultrasound-based viscoelastic imaging. The viscoelastic mechanical properties (viscosity coefficients [Vmax and Vmean] and dispersion coefficients [Dmax and Dmean]) and SWE (Emax) were measured within the tumor and in a 1-mm peritumoral region (Vtmax, Vtmean, et al.). Patients were stratified into high (Ki-67 ≥ 14%) and low (Ki-67 < 14%) proliferation groups. Viscoelastic mechanical properties and SWE between groups were compared.

[RESULTS] Among the 124 female patients with IDC, 94 exhibited high Ki-67 expression while 30 had low Ki-67 expression. No significant differences were observed in SWE-based elasticity between the two groups (p > 0.05). Vmean and Vtmean were lower in the high Ki-67 group (1.1 [0.7-1.7] vs. 1.5 [1.0-2.3], p = 0.020; 1.3 [0.8-1.8] vs. 1.7 [1.1-2.4], p = 0.026, respectively). Using Vmean ≤ 1.2 Pa·s as cutoff value, a significantly higher proportion of high Ki-67 expression was found (64.9% vs. 35.1%, p = 0.016).

[CONCLUSION] Viscoelastic mechanical properties, rather than traditional SWE elasticity, correlated with Ki-67 expression in IDC. A lower Vmean may be correlated with higher proliferative activity, potentially serving as a non-invasive imaging biomarker. These findings support further exploration of ultrasound-based viscoelastic imaging for the assessment of tumor microenvironment heterogeneity.