Objective To explore the relationships of ultrasound vascular index quantification and elastic modulus with biological characteristics of breast cancer and its clinical significance.

Methods A total of 103 patients with breast cancer who received neoadjuvant chemotherapy (NAC) were selected as study subjects. The relationships of the quantification of vascular index (VI) and maximum elastic modulus (E_max) of shear wave elastography (SWE) with the biological characteristics of breast cancer before NAC were analyzed. According to the pathological response of NAC, the patients were divided into significant response group and non-significant response group. The change rates of VI and E_max at the end of different cycles of NAC were compared between the two groups. Receiver operating characteristic (ROC) curve was used to analyze the change rates of VI and E_max at the end of different cycles to predict the pathological response of NAC in breast cancer.

Results Before NAC, VI and E_max were related to the degree of differentiation, pathological stage and HER-2 expression in breast cancer tissues (P < 0.05). The significant response group had higher change rates of VI and E_max at the end of 1, 2, and 4 week of NAC compared to the non-significant response group (P < 0.01). At the end of the second cycle, AUC of change rates of VI combined with E_max predicted the pathological response of NAC in breast cancer was 0.918, with the sensitivity of 0.874, and specificity of 0.905, which were higher than 0.832 of AUC, 0.78 of sensitivity, and 0.827 of specificity at the end of 1 week of NAC, and were higher than 0.853 of AUC, 0.827 of sensitivity, and 0.849 of specificity at the end of the fourth week.

Conclusion VI and E_max are correlated with the degree of differentiation, pathological stage and HER-2 expression in breast cancer. At the end of the second cycle of chemotherapy, the change rates of the VI combined with E_max have the best efficacy in predicting the pathological reaction of NAC in breast cancer.