Purpose: This study evaluated shear wave elastography (SWE) and SWE combined with the Ki-67 index as novel predictive modalities for the pathological response of invasive breast cancer to neoadjuvant chemotherapy (NAC).
Methods: The prospective study recruited 66 eligible patients from July 2014 to November 2015. Tumour stiffness, which corresponds with tumour progression and invasiveness, was assessed by quantitative SWE 1 d before biopsy (time point t0, elasticity E0), 1 d before next NAC cycle (t1-t5, E1-E5), and 1 d before surgery (t6, E6). The relative changes in SWE parameters after the first and second NAC cycles were considered as the variables [ΔE (t1), ΔE (t2)]. The pathological response was classified according to the residual cancer burden (RCB) protocol. Correlations between RCB scores and variables were evaluated. The predictive diagnostic performances of SWE parameters, Ki-67 index, and the predictive RCB (predRCB) score determined by a linear regression model were compared.
Results: Some immunohistochemical and molecular factors and SWE parameters were significantly different among the three RCB groups. The ΔEmean (t2) and Ki-67 had significantly better diagnostic performance than other parameters regarding predicting the pathological response (the RCB-I response and RCB-III resistance). However, the correlation between ΔEmean (t2) and Ki-67 index was significantly weaker as a diagnostic predictor (r = 0.29). We generated a new predictive modality, predRCB, which is a multivariable linear regression model that combines ΔEmean (t2) and the Ki-67 index. The predRCB modality showed better diagnostic performance than SWE parameters and Ki-67 index alone.
Conclusion: Our findings highlight the potential utility for adding the Ki-67 index to the SWE results, which may improve the predictive power of SWE and facilitate personalising the treatment regimens of patients with breast cancer. These results should be validated in the future by performing a multicentre prospective study with a larger cohort.
Keywords: Breast cancer; Ki-67 index; Neoadjuvant chemotherapy; Predict; Shear wave elastography.
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