Stiffness of tumours measured by shear-wave elastography correlated with subtypes of breast cancer

Abstract

Objective: To evaluate the correlation between stiffness values obtained by shear-wave elastography (SWE) and breast cancer subtypes. Methods: This was an institutional review board-approved retrospective study with a waiver of informed consent. The stiffness of 337 invasive breast cancers in 337 women was evaluated by SWE and mean stiffness values (kPa) and qualitative colour scores (1-5) of tumours were obtained. The results were analysed according to BI-RADS category, tumour size, grade and tumour subtype (triple-negative [TN], human epidermal growth factor receptor 2 [HER2]-positive, and oestrogen receptor [ER]-positive) using a multiple linear regression analysis. Results: The mean stiffness values and colour scores were: 146.8 kPa ± 57.0 and 4.1 ± 1.1; 165.8 kPa ± 48.5 and 4.6 ± 0.7 for TN tumours ( n = 64), 160.3 kPa ± 56.2 and 4.3 ± 1.0 for HER2-positive tumours ( n = 55) and 136.9 kPa ± 57.2 and 4.0 ± 1.1 for ER-positive tumours ( n = 218; P < 0.0001). All three breast cancers classified as BI-RADS category 3 on B-mode ultrasound were TN subtype. A multiple linear regression analysis revealed that tumour size, histological grade and tumour subtype were independent factors that influenced the stiffness values. Conclusion: High stiffness values correlated with aggressive subtypes of breast cancer. Key points: ? Shear-wave elastography is increasingly used to measure the stiffness of breast tumours. ? Triple-negative and HER2-positive tumours showed greater stiffness than ER-positive tumours.? All breast cancers classified as BI-RADS 3 on B-mode ultrasound were triple-negative subtype.? Tumour size, histological grade and subtype were independent factors influencing SWE stiffness.