Early Evaluation of Relative Changes in Tumor Stiffness by Shear Wave Elastography Predicts the Response to Neoadjuvant Chemotherapy in Patients With Breast Cancer

Correlation between Baseline Conventional Ultrasounds, Shear-Wave Elastography Indicators, and Neoadjuvant Therapy Efficacy in Triple-Negative Breast Cancer

In patients with triple-negative breast cancer (TNBC)-the subtype with the poorest prognosis among breast cancers-it is crucial to assess the response to the currently widely employed neoadjuvant treatment (NAT) approaches. This study investigates the correlation between baseline conventional ultrasound (US) and shear-wave elastography (SWE) indicators and the pathological response of TNBC following NAT, with a specific focus on assessing predictive capability in the baseline state. This retrospective analysis was conducted by extracting baseline US features and SWE parameters, categorizing patients based on postoperative pathological grading. A univariate analysis was employed to determine the relationship between ultrasound indicators and pathological reactions. Additionally, we employed a receiver operating characteristic (ROC) curve analysis and multivariate logistic regression methods to evaluate the predictive potential of the baseline US indicators. This study comprised 106 TNBC patients, with 30 (28.30%) in a nonmajor histological response (NMHR) group and 76 (71.70%) in a major histological response (MHR) group. Following the univariate analysis, we found that T staging, dmax values, volumes, margin changes, skin alterations (i.e., thickening and invasion), retromammary space invasions, and supraclavicular lymph node abnormalities were significantly associated with pathological efficacy (p < 0.05). Combining clinical information with either US or SWE independently yielded baseline predictive abilities, with AUCs of 0.816 and 0.734, respectively. Notably, the combined model demonstrated an improved AUC of 0.827, with an accuracy of 76.41%, a sensitivity of 90.47%, a specificity of 55.81%, and statistical significance (p < 0.01). The baseline US and SWE indicators for TNBC exhibited a strong relationship with NAT response, offering predictive insights before treatment initiation, to a considerable extent.

The potential role of combined shear wave elastography and superb microvascular imaging for early prediction the pathological response to neoadjuvant chemotherapy in breast cancer

Objectives

The potential role of shear wave elastography (SWE) and superb microvascular imaging (SMI) for early assessment of treatment response to neoadjuvant chemotherapy (NAC) in breast cancer remains unexplored. This study aimed to identify potential factors associated with the pathological response to NAC using these advanced ultrasound techniques.

Methods

Between August 2021 and October 2022, 68 patients with breast cancer undergoing NAC were recruited. Patients underwent conventional ultrasonography, SMI, and SWE examinations at baseline and post-2nd cycle of NAC. Maximum tumor diameter (Dmax), maximum elastic value (Emax), peak systolic velocity (PSV), and resistance index (RI) at baseline and the rate of change of these parameters post-2nd cycle were recorded. After chemotherapy, all patients underwent surgery. Using the Miller-Payne's grade, patients were categorized into response (grades 3, 4, or 5) and non-response (grades 1 or 2) group. Parameters were compared using t-tests at baseline and post-2nd cycle. Binary logistic regression analysis was used to identify variables and their odds ratios (ORs) related to responses and a prediction model was established. ROC curves were drawn to analyze the efficacy of each parameter and their combined model for early NAC response prediction.

Results

Among the 68 patients, 15(22.06%) were categorized into the non-response group, whereas 53(77.94%) were categorized into the response group. At baseline, no significant differences were observed between the two groups (p>0.05). Post-2nd cycle of NAC, rates of change of Emax, PSV and RI (ΔEmax, ΔPSV and ΔRI) were higher in responders than non-responders (p<0.05). Binary logistic regression analysis revealed that ΔEmax (OR 0.797 95% CI, 0.683-0.929), ΔPSV (OR 0.926, 95%CI, 0.860-0.998), and ΔRI (OR 0.841, 95%CI, 0.736-0.960) were independently associated with the pathological response of breast cancer after NAC. The combined prediction model exhibited higher accuracy in the early evaluation of the response to NAC (AUC 0.945, 95%CI, 0.873-1.000).

Conclusion

SWE and SMI techniques enable early identification of tumor characteristics associated with the pathological response to NAC and may be potentially indicative of an effective response. These factors may eventually be used for the early assessment of NAC treatment for clinical management.

Tumor matrix stiffness provides fertile soil for cancer stem cells

Matrix stiffness is a mechanical characteristic of the extracellular matrix (ECM) that increases from the tumor core to the tumor periphery in a gradient pattern in a variety of solid tumors and can promote proliferation, invasion, metastasis, drug resistance, and recurrence. Cancer stem cells (CSCs) are a rare subpopulation of tumor cells with self-renewal, asymmetric cell division, and differentiation capabilities. CSCs are thought to be responsible for metastasis, tumor recurrence, chemotherapy resistance, and consequently poor clinical outcomes. Evidence suggests that matrix stiffness can activate receptors and mechanosensor/mechanoregulator proteins such as integrin, FAK, and YAP, modulating the characteristics of tumor cells as well as CSCs through different molecular signaling pathways. A deeper understanding of the effect of matrix stiffness on CSCs characteristics could lead to development of innovative cancer therapies. In this review, we discuss how the stiffness of the ECM is sensed by the cells and how the cells respond to this environmental change as well as the effect of matrix stiffness on CSCs characteristics and also the key malignant processes such as proliferation and EMT. Then, we specifically focus on how increased matrix stiffness affects CSCs in breast, lung, liver, pancreatic, and colorectal cancers. We also discuss how the molecules responsible for increased matrix stiffness and the signaling pathways activated by the enhanced stiffness can be manipulated as a therapeutic strategy for cancer.

Diagnostic Performance of Strain and Shear Wave Elastography for the Response to Neoadjuvant Chemotherapy in Breast Cancer Patients: Systematic Review and Meta-Analysis

OBJECTIVES

To investigate the diagnostic performance of strain and shear wave elastography for the response to neoadjuvant chemotherapy (NAC) in breast cancer patients.

METHODS

Relevant studies were searched in the databases of PubMed, Web of Science and Cochrane Library until October 2021. The diagnostic performance of ultrasonic elastography for the response to NAC were estimated by calculating the area under the curve (AUC) with sensitivity and specificity using Stata 14.0.

RESULTS

A total of 15 studies that comprise 1147 breast cancer patients were included in this meta-analysis. The pooled AUC of strain elastography in diagnosing responses were 0.89 (95% CI = 0.86-0.91) with 87% (95% CI = 75-94%) of sensitivity and 80% (95% CI = 72-84%) of specificity. The pooled AUC of shear wave elastography in diagnosing response were 0.82 (95% CI = 0.78-0.85) with 79% (95% CI = 72-84%) of sensitivity and 81% (95% CI = 71-88%). No publication bias was observed across the studies using Deek's funnel plot.

CONCLUSIONS

Based on current evidence, this meta-analysis confirmed that strain and shear wave elastography exhibited favorable performance for predicting responses to NAC. Strain and shear wave elastography may be a useful, noninvasive method for the assessment of response to NAC in breast cancer patients.

Ultrasound Strain Elastography and Contrast-Enhanced Ultrasound in Predicting the Efficacy of Neoadjuvant Chemotherapy for Breast Cancer: A Nomogram Integrating Ki-67 and Ultrasound Features

OBJECTIVES

To explore whether conventional elastography and contrast-enhanced ultrasound (CEUS) combined with histopathology can monitor the efficacy of neoadjuvant chemotherapy (NAC) for breast cancer (BC), and develop a Nomogram prediction model monitoring response to NAC.

METHODS

From February 2010 to November 2015, 91 BC patients who received NAC were recruited. The maximum diameter, stiffness, and CEUS features were assessed. Core biopsy, surgical pathology immunophenotype, and Miller-Payne (MP) evaluation were documented. Univariate and multivariate analysis was performed using receiver operating characteristic (ROC) analysis and logistic regression analysis.

RESULTS

There were 37 cases showing pathological complete response (pCR) and 54 of non-pCR. The changes of maximal diameter were correlated with MP (P < .05). The sensitivity (SEN), specificity (SPE), and area under the ROC curve (AUC) of baseline size predicting pCR were 57.40%, 70.30%, and 0.64 (P = .024). Baseline Ki-67 index of pCR group is significantly higher than that of non-pCR group (P = .029), and the ROC analysis of baseline Ki-67 indicates the SEN, SPE, and AUC of 51.70%, 78.00%, and 0.638 (P = .050). When combined with size, CEUS features, stiffness, and Ki-67 of baseline, the ROC curve shows good performance with SEN, SPE, and AUC of 70.00%, 76.19%, 0.821 (P = .004). Incorporating the change of characteristics into multivariate regression analysis, the results demonstrate excellent performance (SEN 100.00%, SPE 95.24%, AUC 0.986, P = .000).

CONCLUSIONS

The change of the maximum size was correlated with MP score, which can provide reference to predict efficacy of NAC and evaluate residual lesions. When combining with elastography, CEUS, and Ki-67, better performance in predicting pathological response was shown.

Potential value of tumor stiffness and sE-cadherin in predicting the response to neoadjuvant therapy in HER2-positive breast cancers

Background: This prospective study compared the diagnostic value of tumor stiffness and serum soluble E-cadherin (sE-cadherin) expression for predicting response to neoadjuvant therapy in HER2-positive breast cancers. Methods: 112 patients with early or locally advanced HER2-positive breast cancer were enrolled. Maximum stiffness (Emax), mean stiffness (Emean) and their relative changes were assessed at t0 and t2. sE-cadherin levels were analyzed using ELISA. Pathological complete response was defined as no invasive disease in the breast and axilla (ypT0/is, ypN0) after surgery. The ability of tumor stiffness, sE-cadherin and the combination of ΔEmean (the relative change in Emean after the second cycle of neoadjuvant therapy) and sE-cadherin in predicting tumor responses was assessed using receiver operating characteristic curves and the Z-test. Results: Tumor stiffness and sE-cadherin decreased during neoadjuvant therapy. ΔEmean and sE-cadherin revealed the best predictive performance, with areas under the curve (AUCs) of 0.843 and 0.857, respectively. No significant differences in AUCs were reported between ΔEmean and sE-cadherin (p = 0.795). The combined use of ΔEmean and sE-cadherin showed the highest sensitivity and specificity (93.22 and 90.57%, respectively), with an AUC of 0.937. Conclusion: The combination of ΔEmean and sE-cadherin may improve the predictive power of each single factor. Although further verification is required, this study may promote noninvasive prediction of neoadjuvant therapy responses and help personalize the treatment regimen.

Evaluation of change in tumor stiffness measured by acoustic radiation force impulse imaging for early prediction of response to neoadjuvant chemotherapy in breast cancer

OBJECTIVES

In this study, the role of change in tumor stiffness between pre- and post-two cycles of neoadjuvant chemotherapy (NACT) measured by Acoustic Radiation Force Impulse (ARFI) imaging for predicting the response to NACT in breast cancer was analyzed.

METHODS

Fifty-two adult women with biopsy-proven locally advanced breast cancer and early-stage breast cancer who received NACT followed by either modified radical mastectomy or breast conservation surgery were included in the study. Tumor stiffness represented by shear wave velocity (SWV) in meter per second by ARFI imaging was measured before and after two cycles of NACT. Participants were categorized into responders and nonresponders based on pathological response assessment from the postoperative specimen. The association of change in tumor stiffness between pre- and post-two cycles of NACT with final pathological response status was assessed.

RESULTS

The mean change in SWV before and after completion of two cycles of NACT was 0.42 ± 0.16 and 0.17 ± 0.11 m/s in responders and nonresponders, respectively, and this difference was proven to be statistically significant (p < 0.001) suggesting that tumors that exhibit a larger reduction in tumor stiffness, respond better. An SWV reduction cut-off of 0.295 m/s between baseline and post-two cycles of NACT was also arrived at, which can discriminate between responders and nonresponders with a sensitivity and specificity of 88% and 83%, respectively.

CONCLUSION

Difference in tumor stiffness measured by ARFI imaging before and after two cycles of chemotherapy can be used as a reliable early predictor of response to chemotherapy in breast cancer.

Advances in Imaging in Evaluating the Efficacy of Neoadjuvant Chemotherapy for Breast Cancer

Neoadjuvant chemotherapy (NAC) is increasingly widely used in breast cancer treatment, and accurate evaluation of its response provides essential information for treatment and prognosis. Thus, the imaging tools used to quantify the disease response are critical in evaluating and managing patients treated with NAC. We discussed the recent progress, advantages, and disadvantages of common imaging methods in assessing the efficacy of NAC for breast cancer.

Evaluation of Different Types of Breast Lesions With Apparent Diffusion Coefficient and Shear Wave Elastography Values: Comparison of Shear Wave Elastography and Apparent Diffusion Coefficient in Breast Lesions

Objective:

The aim of this study was to compare the stiffness of different histological types of breast lesions by obtaining shear wave elastography (SWE) and apparent diffusion coefficient (ADC) values, and to determine the contribution of these two methods to the diagnosis.

Materials and Methods:

In total, 70 patients with biopsy-proven breast lesions were included in the study. The mean SWE values of breast lesions were recorded and ADC values of these lesions were calculated. Receiver operating characteristic (ROC) curve analyses and the diagnostic accuracies of SWE-ADC values were determined.

Results:

The mean SWE values were 45.47 ± 25.11 kPa and 3.51 ± 1.04 m/s in benign group, and 161.11 ± 219.34 kPa and 5.96 ± 1.06 m/s in malignant group, respectively. The mean ADC values were 1.38 ± 0.32 (×10–3 mm2/s) in benign group and 0.96 ± 0.22 (×10–3 mm2/s) in malignant group, respectively. When the diagnostic performances of both imaging modalities on mass stiffness are evaluated, statistically significant negative correlations were found between SWE lesion values and ADC lesion values.

Conclusion:

Evaluation of tissue elasticity has recently been used frequently in the diagnosis of breast diseases. SWE-ADC values, which are negatively correlated in the diagnosis of breast masses, may prove to be a powerful alternative diagnostic tool that can be used interchangeably, as appropriate.

Accuracy of ultrasound elastography for predicting breast cancer response to neoadjuvant chemotherapy: A systematic review and meta-analysis

BACKGROUND

Several studies have reported the prognostic value of ultrasound elastography (UE) in patients receiving neoadjuvant chemotherapy (NACT) for breast cancer. However, the assessment of parameters differed between shear-wave elastography and strain elastography in terms of measured elasticity parameter and mode of imaging. It is important, therefore, to assess the accuracy of the two modes of elastography.

AIM

To assess the accuracy of UE for predicting the pathologic complete response (pCR) in breast cancer patients following NACT.

METHODS

A comprehensive and systematic search was performed in the databases of MEDLINE, EMBASE, SCOPUS, PubMed Central, CINAHL, Web of Science and Cochrane library from inception until December 2020. Meta-analysis was performed using STATA software “Midas” package.

RESULTS

A total of 14 studies with 989 patients were included. The pooled sensitivities were 86% [95% confidence interval (CI): 76%-92%] for UE, 77% (95%CI: 68%-84%) for shear-wave elastography, and 92% (95%CI: 73%-98%) for strain-wave elastography. The pooled score specificities were 86% (95%CI: 80%-90%) for UE, 84% (95%CI: 72%-91%) for shear-wave elasticity, and 87% (95%CI: 81%-92%) for strain-wave elastography. A significant heterogeneity was found among studies based on the chi-square test results and an I² statistic > 75%.

CONCLUSION

Strain-wave type of UE can accurately predict the pCR following NACT amongst breast cancer patients. Studies exploring its accuracy in different ethnic populations are required to strengthen the evidence.

Combining conventional ultrasound and sonoelastography to predict axillary status after neoadjuvant chemotherapy for breast cancer

OBJECTIVE

To determine the ability of conventional ultrasound (US) combined with shear wave elastography (SWE) to reveal axillary status after neoadjuvant chemotherapy (NAC) in breast cancer patients.

METHODS

From September 2016 to December 2021, 201 patients with node-positive breast cancer who underwent NAC were enrolled in this prospective study. Conventional US features of axillary lymph nodes and SWE characteristics of breast lesions after NAC were analyzed. The diagnostic performances of US, SWE, and their combination were assessed using multivariate logistic regression and receiver operator characteristic curve (ROC) analyses.

RESULTS

The area under the ROC curve (AUC) for the ability of conventional US features to determine axillary status after NAC was 0.82, with a sensitivity of 85.23%, a specificity of 67.39%, and an accuracy of 76.11%. Shear wave velocity (SWV) displayed moderate performance for predicting axilla status after NAC with SWV_mean demonstrating an AUC of 0.85. Cortical thickness and shape of axillary nodes and SWV_mean of breast tumors were independently associated with axillary nodal metastasis after NAC. Compared to conventional US, the combination of conventional US of axillary lymph nodes with SWE of breast lesions achieved a significantly higher AUC (0.90 vs 0.82, p < 0.01, Delong's test) with a sensitivity of 87.50%, improved specificity of 82.61% and accuracy of 85.00%.

CONCLUSIONS

Breast SWE was independently associated with residual metastasis of axillary node after NAC in patients with initially diagnosed positive axilla. Combining SWE with conventional US showed good diagnostic performance for axillary node disease after NAC.

KEY POINTS

• Breast SWE can serve as a supplement to axilla US for the evaluation of the axilla after NAC. • The combination of axilla US with breast SWE may be a promising method to facilitate less-invasive treatment in patients receiving NAC.

Neoadjuvant approach in patients with early breast cancer: patient assessment, staging, and planning

Neoadjuvant treatment (NAT) has become an option in early stage (stage I-II) breast cancer (EBC). New advances in systemic and targeted therapies have increased rates of pathologic complete response increasing the number of patients undergoing NAT. Clear benefits of NAT are downstaging the tumor and the axillary nodes to de-escalate surgery and to evaluate response to treatment. Selection of patients for NAT in EBC rely in several factors that are related to patient characteristics (i.e, age and comorbidities), to tumor histology, to stage at diagnosis and to the potential changes in surgical or adjuvant treatments when NAT is administered.

Imaging and histologic confirmation is performed to assess extent of disease y to confirm diagnosis. Besides mammogram and ultrasound, functional breast imaging MRI has been incorporated to better predict treatment response and residual disease. Contrast enhanced mammogram (CEM), shear wave elastography (SWE), or Dynamic Optical Breast Imaging (DOBI) are emerging techniques under investigation for assessment of response to neoadjuvant therapy as well as for predicting response. Surgical plan should be delineated after NAT taking into account baseline characteristics, tumor response and patient desire.

In the COVID era, we have witnessed also the increasing use of NAT in patients who may be directed to surgery, unable to have it performed as surgery has been reserved for emergency cases only.

Softening redox homeostasis in cancer cells

Extracellular matrix (ECM) rigidity increases during tumour progression. In a recent study, Romani et al. delineated a connection between ECM stiffness and the redox response of disseminated tumour cells. Their results suggest that soft ECM promotes DRP1-mediated mitochondrial fission and an NRF2-dependent antioxidant response.

Mitochondrial fission links ECM mechanotransduction to metabolic redox homeostasis and metastatic chemotherapy resistance

Metastatic breast cancer cells disseminate to organs with a soft microenvironment. Whether and how the mechanical properties of the local tissue influence their response to treatment remains unclear. Here we found that a soft extracellular matrix empowers redox homeostasis. Cells cultured on a soft extracellular matrix display increased peri-mitochondrial F-actin, promoted by Spire1C and Arp2/3 nucleation factors, and increased DRP1- and MIEF1/2-dependent mitochondrial fission. Changes in mitochondrial dynamics lead to increased production of mitochondrial reactive oxygen species and activate the NRF2 antioxidant transcriptional response, including increased cystine uptake and glutathione metabolism. This retrograde response endows cells with resistance to oxidative stress and reactive oxygen species-dependent chemotherapy drugs. This is relevant in a mouse model of metastatic breast cancer cells dormant in the lung soft tissue, where inhibition of DRP1 and NRF2 restored cisplatin sensitivity and prevented disseminated cancer-cell awakening. We propose that targeting this mitochondrial dynamics- and redox-based mechanotransduction pathway could open avenues to prevent metastatic relapse.

Predicting Pathological Complete Response After Neoadjuvant Chemotherapy in Advanced Breast Cancer by Ultrasound and Clinicopathological Features Using a Nomogram

Background and Aims

Prediction of pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) for breast cancer is critical for surgical planning and evaluation of NAC efficacy. The purpose of this project was to assess the efficiency of a novel nomogram based on ultrasound and clinicopathological features for predicting pCR after NAC.

Methods

This retrospective study included 282 patients with advanced breast cancer treated with NAC from two centers. Patients received breast ultrasound before NAC and after two cycles of NAC; and the ultrasound, clinicopathological features and feature changes after two cycles of NAC were recorded. A multivariate logistic regression model was combined with bootstrapping screened for informative features associated with pCR. Then, we constructed two nomograms: an initial-baseline nomogram and a two-cycle response nomogram. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were analyzed. The C-index was used to evaluate predictive accuracy.

Results

Sixty (60/282, 21.28%) patients achieved pCR. Triple-negative breast cancer (TNBC) and HER2-amplified types were more likely to obtain pCR. Size shrinkage, posterior acoustic pattern, and elasticity score were identified as independent factors by multivariate logistic regression. In the validation cohort, the two-cycle response nomogram showed better discrimination than the initial-baseline nomogram, with the C-index reaching 0.79. The sensitivity, specificity, and NPV of the two-cycle response nomogram were 0.77, 0.77, and 0.92, respectively.

Conclusion

The two-cycle response nomogram exhibited satisfactory efficiency, which means that the nomogram was a reliable method to predict pCR after NAC. Size shrinkage after two cycles of NAC was an important in dependent factor in predicting pCR.

A Narrative Review of Ultrasound Technologies for the Prediction of Neoadjuvant Chemotherapy Response in Breast Cancer

The incidence and mortality rate of breast cancer (BC) in women currently ranks first worldwide, and neoadjuvant chemotherapy (NAC) is widely used in patients with BC. A variety of imaging assessment methods have been used to predict and evaluate the response to NAC. Ultrasound (US) has many advantages, such as being inexpensive and offering a convenient modality for follow-up detection without radiation emission. Although conventional grayscale US is typically used to predict the response to NAC, this approach is limited in its ability to distinguish viable tumor tissue from fibrotic scar tissue. Contrast-enhanced ultrasound (CEUS) combined with a time-intensity curve (TIC) not only provides information on blood perfusion but also reveals a variety of quantitative parameters; elastography has the potential capacity to predict NAC efficiency by evaluating tissue stiffness. Both CEUS and elastography can greatly improve the accuracy of predicting NAC responses. Other US techniques, including three-dimensional (3D) techniques, quantitative ultrasound (QUS) and US-guided near-infrared (NIR) diffuse optical tomography (DOT) systems, also have advantages in assessing NAC response. This paper reviews the different US technologies used for predicting NAC response in BC patients based on the previous literature.

Tumor stiffness measured by shear-wave elastography: association with disease-free survival in women with early-stage breast cancer

OBJECTIVE

To determine whether shear-wave elastography (SWE)-measured tumor stiffness is associated with disease-free survival in females with early-stage invasive breast cancer.

METHODS

This retrospective study included 202 consecutive females (mean age, 52.9 years; range, 25-84 years) with newly diagnosed T1-two breast cancer who underwent preoperative SWE between April 2015 and January 2016. Tumor stiffness was assessed and quantitative SWE features of each breast lesion were obtained by a breast radiologist. Cox proportional hazard models were used to identify associations between SWE features and disease-free survival after adjusting for clinicopathologic factors.

RESULTS

Fifteen (7.4%) patients exhibited recurrence after a median follow-up of 56 months. Mean (Emean), minimum, and maximum elasticity values were higher in females with recurrence than in those without recurrence (184.4, 138.3, and 210.5 kPa vs 134.9, 101.7, and 159.8 kPa, respectively; p = 0.005, p = 0.005, and p = 0.012, respectively). Receiver operating characteristics curve analysis for prediction of recurrence showed that Emean yielded the largest area under the curve (0.717) among the quantitative SWE parameters, and the optimal cut-off value was 121.7 kPa. Multivariable Cox proportional hazards analysis revealed that higher Emean (>121.7 kPa) [adjusted hazard ratio (HR), 10.01; 95% CI: 1.31-76.33; p = 0.026] and lymphovascular invasion (adjusted HR, 7.72; 95% CI: 1.74-34.26; p = 0.007) were associated with worse disease-free survival outcomes.

CONCLUSION

Higher SWE-measured Emean was associated with worse disease-free survival in females with early-stage invasive breast cancer.

ADVANCES IN KNOWLEDGE

Tumor stiffness assessed with shear-wave elastography might serve as a quantitative imaging biomarker of disease-free survival in females with T1-two breast cancer.

Non-Invasive Ultrasonic Description of Tumor Evolution

Simple Summary

During tumor evolution, heterogeneous structural and functional changes occur in the tumor microenvironment. These complex changes have pro- or anti-tumorigenesis effects and have an impact on therapy efficiency. Therefore, the tumor microenvironment needs to be non-invasively characterized over time. The aim of this preclinical work is to compare the sensitivity of modifications occurring during tumor evolution of volume, immunohistochemistry and non-invasive quantitative ultrasound parameters (Shear Wave Elastography and dynamic Contrast-Enhanced Ultrasound) and to study the link between them. The complementary evaluation over time of multiple morphological and functional parameters during tumor growth underlines the need to integrate histological, morphological, functional, and, ultimately, genomic information into models that can consider the temporal and spatial variability of features to better understand tumor evolution.

Abstract

Purpose: There is a clinical need to better non-invasively characterize the tumor microenvironment in order to reveal evidence of early tumor response to therapy and to better understand therapeutic response. The goals of this work are first to compare the sensitivity to modifications occurring during tumor growth for measurements of tumor volume, immunohistochemistry parameters, and emerging ultrasound parameters (Shear Wave Elastography (SWE) and dynamic Contrast-Enhanced Ultrasound (CEUS)), and secondly, to study the link between the different parameters. Methods: Five different groups of 9 to 10 BALB/c female mice with subcutaneous CT26 tumors were imaged using B-mode morphological imaging, SWE, and CEUS at different dates. Whole-slice immunohistological data stained for the nuclei, T lymphocytes, apoptosis, and vascular endothelium from these tumors were analyzed. Results: Tumor volume and three CEUS parameters (Time to Peak, Wash-In Rate, and Wash-Out Rate) significantly changed over time. The immunohistological parameters, CEUS parameters, and SWE parameters showed intracorrelation. Four immunohistological parameters (the number of T lymphocytes per mm² and its standard deviation, the percentage area of apoptosis, and the colocalization of apoptosis and vascular endothelium) were correlated with the CEUS parameters (Time to Peak, Wash-In Rate, Wash-Out Rate, and Mean Transit Time). The SWE parameters were not correlated with the CEUS parameters nor with the immunohistological parameters. Conclusions: US imaging can provide additional information on tumoral changes. This could help to better explore the effect of therapies on tumor evolution, by studying the evolution of the parameters over time and by studying their correlations.

Pancreatic Ductal Adenocarcinoma: Relating Biomechanics and Prognosis

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and carries a dismal prognosis. Resectable patients are treated predominantly with surgery while borderline resectable patients may receive neoadjuvant treatment (NAT) to downstage their disease prior to possible resection. PDAC tissue is stiffer than healthy pancreas, and tissue stiffness is associated with cancer progression. Another feature of PDAC is increased tissue heterogeneity. We postulate that tumour stiffness and heterogeneity may be used alongside currently employed diagnostics to better predict prognosis and response to treatment. In this review we summarise the biomechanical changes observed in PDAC, explore the factors behind these changes and describe the clinical consequences. We identify methods available for assessing PDAC biomechanics ex vivo and in vivo, outlining the relative merits of each. Finally, we discuss the potential use of radiological imaging for prognostic use.

Bioprintable, Stiffness-Tunable Collagen-Alginate Microgels for Increased Throughput 3D Cell Culture Studies

3D culture platforms with tunable stiffness have the potential to improve many applications, such as drug discovery, organoid studies, and stem cell differentiation. Both dimensionality and stiffness regulate crucial and relevant cellular processes. However, 3D culture models are often limited in throughput and difficult to adopt for widespread use. Here, we demonstrate an accessible 3D, stiffness-tunable tissue culture platform, based on an interpenetrating network of collagen-1 and alginate. When blended with polymers that induce phase separation, these networks can be bioprinted at microliter volumes, using standard liquid handling infrastructure. We demonstrate robust reproducibility in printing these microgels, consistent tunability of mechanical properties, and maintained viability of multiple printed cell types. To highlight the utility and importance of this system, we demonstrate distinct morphological changes to cells in culture, use the system to probe the role of matrix mechanics and soluble factors in a collagen contraction assay, and perform a prototype viability screen against a candidate chemotherapeutic, demonstrating stiffness-dependent responses.

Early assessment of shear wave elastography parameters foresees the response to neoadjuvant chemotherapy in patients with invasive breast cancer

BACKGROUND

Early prediction of tumor response to neoadjuvant chemotherapy (NACT) is crucial for optimal treatment and improved outcome in breast cancer patients. The purpose of this study is to investigate the role of shear wave elastography (SWE) for early assessment of response to NACT in patients with invasive breast cancer.

METHODS

In a prospective study, 62 patients with biopsy-proven invasive breast cancer were enrolled. Three SWE studies were conducted on each patient: before, at mid-course, and after NACT but before surgery. A new parameter, mass characteristic frequency (fmass), along with SWE measurements and mass size was obtained from each SWE study visit. The clinical biomarkers were acquired from the pre-NACT core-needle biopsy. The efficacy of different models, generated with the leave-one-out cross-validation, in predicting response to NACT was shown by the area under the receiver operating characteristic curve and the corresponding sensitivity and specificity.

RESULTS

A significant difference was found for SWE parameters measured before, at mid-course, and after NACT between the responders and non-responders. The combination of Emean2 and mass size (s2) gave an AUC of 0.75 (0.95 CI 0.62-0.88). For the ER+ tumors, the combination of Emean_ratio1, s1, and Ki-67 index gave an improved AUC of 0.84 (0.95 CI 0.65-0.96). For responders, fmass was significantly higher during the third visit.

CONCLUSIONS

Our study findings highlight the value of SWE estimation in the mid-course of NACT for the early prediction of treatment response. For ER+ tumors, the addition of Ki-67improves the predictive power of SWE. Moreover, fmass is presented as a new marker in predicting the endpoint of NACT in responders.

Predicting Response to Neoadjuvant Chemotherapy in Locally Advanced Breast Cancer After the Second Cycle of Chemotherapy Using Shear-Wave Elastography-A Preliminary Evaluation

ABSTRACT

The primary objective of the study was to determine whether shear wave elastography can be used to predict the response of neoadjuvant chemotherapy (NACT) in women having invasive breast cancer. A prospective study involving 28 patients having invasive breast cancer and undergoing NACT followed by surgery was done after institutional review board approval. All the patients underwent 2-dimensional B-mode ultrasound and 2-dimensional shear wave elastography before the start of chemotherapy and after 2 cycles of completion of chemotherapy, and mean stiffness was recorded. The patients were segregated to responders and nonresponders based on residual cancer burden scoring. Difference in mean elasticity was compared between the 2 groups. The results showed that the mean stiffness after 2 cycles was significantly different between the responders and nonresponders and so was the change in the mean stiffness after 2 cycles of NACT. Using a cutoff value of 45.5 kPa (20.53%), change in mean elasticity after 2 cycles of NACT, sensitivity of 76.9%, and specificity of 80% with negative predictive value of 80.1 was attained. Responders show greater change in mean stiffness after 2 cycles of NACT as compared with nonresponders on shear wave elastography; thus, it can be used to predict response to NACT after 2 cycles.

Tumor stiffness measured by shear wave elastography correlates with tumor hypoxia as well as histologic biomarkers in breast cancer

Background

Shear wave elastography (SWE) is an ultrasound technique for the noninvasive quantification of tissue stiffness. The hypoxic tumor microenvironment promotes tumor stiffness and is associated with poor prognosis in cancer. We aimed to investigate the correlation between tumor hypoxia and histologic biomarkers and tumor stiffness measured by SWE in breast cancer.

Methods

From June 2016 to January 2018, 82 women with invasive breast cancer who underwent SWE before treatment were enrolled. Average tumor elasticity (E_average) and tumor-to-fat elasticity ratio (E_ratio) were extracted from SWE. Immunohistochemical staining of glucose transporter 1 (GLUT1) was used to assess tumor hypoxia in breast cancer tissues and automated digital image analysis was performed to assess GLUT1 activities. Spearman correlation and logistic regression analyses were performed to identify associations between GLUT1 expression and SWE values, histologic biomarkers, and molecular subtypes. The Mann–Whitney U test, t test, or Kruskal–Wallis test was used to compare SWE values and histologic features according to the GLUT1 expression (≤the median vs > median).

Results

E_average (r = 0.676) and E_ratio (r = 0.411) correlated significantly with GLUT1 expression (both p <  0.001). E_average was significantly higher in cancers with estrogen receptor (ER)–, progesterone receptor (PR)–, Ki67+, and high-grade (p <  0.05). E_ratio was higher in cancers with Ki67+, lymph node metastasis, and high-grade (p <  0.05). Cancers with high GLUT1 expression (>median) had higher E_average (mean, 85.4 kPa vs 125.5 kPa) and E_ratio (mean, 11.7 vs 17.9), and more frequent ER– (21.7% vs 78.3%), PR– (26.4% vs 73.1%), Ki67+ (31.7%% vs 68.3%), human epidermal growth factor receptor 2 (HER2) + (25.0% vs 75.0%), high-grade (28.6% vs 71.4%), and HER2-overexpressing (25.0% vs 75.0%) and triple-negative (23.1% vs 76.9%) subtypes (p <  0.05). Multivariable analysis showed that E_average was independently associated with GLUT1 expression (p <  0.001).

Conclusions

Tumor stiffness on SWE is significantly correlated with tumor hypoxia as well as histologic biomarkers. In particular, E_average on SWE has independent prognostic significance for tumor hypoxia in the multivariable analysis and can potentially be used as a noninvasive imaging biomarker to predict prognosis and pretreatment risk stratification in breast cancer patients.

Early response and pathological complete remission in Breast Cancer with different molecular subtypes: a retrospective single center analysis

Purpose: To evaluate the association of clinical early response and pathological complete remission (pCR) in breast cancer patients with different molecular subtypes.

Materials and methods: Breast cancer patients who received neoadjuvant treatment (NAT) with clinical early response assessment from October 2008 to October 2018 were retrospectively analyzed. Clinical early response was defined as tumor size decreasing ≥30% evaluated by ultrasound after two cycles of NAT. Chi-square test was used to compare the pCR rates between the responder and non-responder groups with different molecular subtypes. Multivariate logistic regression was used to identify independent factors associated with the pCR.

Results: A total of 328 patients were included: 100 responders and 228 non-responders. The progesterone receptor (PR) expression was an independent factor associated with clinical early response (OR=2.39, 95%CI=1.41-4.05, P=0.001). The pCR rate of breast was 50.0% for responders and 18.0% for non-responders (P<0.001). Regarding different molecular subtypes, responders had higher pCR rates than non-responders for patients with HER2 overexpression (OR=10.66, 95%CI=2.18-52.15, P=0.001), triple negative (OR=3.29, 95%CI=1.23-8.84, P=0.016) and Luminal (HER2-) subtypes (OR=8.58, 95%CI=3.05-24.10, P<0.001) respectively. Moreover, pCR rate can be achieved as high as 88.2% in HER2 overexpression patients with early clinical response, which was significantly higher than patients without early response (41.3%, P=0.001). Multivariate analysis showed that clinical early response was an independent factor associated with the pCR rate (OR=4.87, 95%CI=2.72-8.72, P<0.001).

Conclusions: Early response was significantly associated with a higher pCR rate in breast cancer patients receiving NAT, especially for patients with HER2 overexpression subtype, which warrants further clinical evaluation.

Prediction of pathological complete response in breast cancer patients during neoadjuvant chemotherapy: Is shear wave elastography a useful tool in clinical routine?

OBJECTIVE

To compare the validity of Shear Wave Elastography (SWE) for the preoperative assessment of pathological complete response (pCR) to standard clinical assessment in breast cancer patients undergoing neoadjuvant chemotherapy (NACT).

MATERIALS AND METHODS

This prospective, consecutive clinical trial was conducted under routine clinical practice. Analysis included 134 patients. SWE served as index test, final pathology from surgical specimen as reference standard. PCR (ypT0) was defined as primary endpoint. Elasticity changes were compared for the pCR- vs. non-pCR group. To determine the validity of shear wave velocity (V_s), ROC analyses and diagnostic accuracy parameters were calculated and compared to the final standard clinical assessment by physical examination, mammography and B-mode ultrasound (ycT + vs. ycT0).

RESULTS

V_s was significantly reduced in pCR and non-pCR groups during NACT (pCR: ΔV_s(abs) = 3.90 m/s, p < 0.001; non-pCR: ΔV_s(abs) = 3.10 m/s, p < 0.001). The pCR-group showed significant lower V_s for all control visits (t_1,2,END: p < 0.001). ROC analysis of V_s yielded moderate AUCs for the total population (t₀: 0.613, t₁: 0.745, t₂: 0.685, t_END: 0.718). Compared to standard clinical assessment, V_s(t_END) (cut-off: ≤3.35 m/s) was superior in sensitivity (79.6 % vs. 54.5 %), NPV (86.4 % vs. 77.5 %), FNR (20.4 % vs. 45.5 %), inferior in specificity (58.6 % vs. 77.5 %), PPV (46.3 % vs. 54.5 %), FPR (41.4 % vs. 22.5 %).

CONCLUSION

SWE measures significant differences in tumour elasticity changes in pCR vs. non-pCR cases. SWE shows improved sensitivity compared to standard clinical assessment, high NPV and low FNR, but failed in specificity in order to predict pCR under routine conditions.

Harmonic Motion Imaging of Pancreatic Tumor Stiffness Indicates Disease State and Treatment Response

PURPOSE

Pancreatic ductal adenocarcinoma (PDA) is a common, deadly cancer that is challenging both to diagnose and to manage. Its hallmark is an expansive, desmoplastic stroma characterized by high mechanical stiffness. In this study, we sought to leverage this feature of PDA for two purposes: differential diagnosis and monitoring of response to treatment.

EXPERIMENTAL DESIGN

Harmonic motion imaging (HMI) is a functional ultrasound technique that yields a quantitative relative measurement of stiffness suitable for comparisons between individuals and over time. We used HMI to quantify pancreatic stiffness in mouse models of pancreatitis and PDA as well as in a series of freshly resected human pancreatic cancer specimens.

RESULTS

In mice, we learned that stiffness increased during progression from preneoplasia to adenocarcinoma and also effectively distinguished PDA from several forms of pancreatitis. In human specimens, the distinction of tumors versus adjacent pancreatitis or normal pancreas tissue was even more stark. Moreover, in both mice and humans, stiffness increased in proportion to tumor size, indicating that tuning of mechanical stiffness is an ongoing process during tumor progression. Finally, using a brca2-mutant mouse model of PDA that is sensitive to cisplatin, we found that tissue stiffness decreases when tumors respond successfully to chemotherapy. Consistent with this observation, we found that tumor tissues from patients who had undergone neoadjuvant therapy were less stiff than those of untreated patients.

CONCLUSIONS

These findings support further development of HMI for clinical applications in disease staging and treatment response assessment in PDA.

Monitoring the response to neoadjuvant chemotherapy in patients with breast cancer using ultrasound scattering coefficient: A preliminary report

Objective: Neoadjuvant chemotherapy was initially used in locally advanced breast cancer, and currently it is recommended for patients with Stage 3 and with early-stage disease with human epidermal growth factor receptors positive or triple-negative breast cancer. Ultrasound imaging in combination with a quantitative ultrasound method is a novel diagnostic approach. Aim of study: The aim of this study was to analyze the variability of the integrated backscatter coefficient, and to evaluate their use to predict the effectiveness of treatment and compare to ultrasound examination results. Material and method: Ten patients (mean age 52.9) with 13 breast tumors (mean dimension 41 mm) were selected for neoadjuvant chemotherapy. Ultrasound was performed before the treatment and one week after each course of neoadjuvant chemotherapy. The dimensions were assessed adopting the RECIST criteria. Tissue responses were classified as pathological response into the following categories: not responded to the treatment (G1, cell reduction by ≤9%) and responded to the treatment partially: G2, G3, G4, cell reduction by 10-29% (G2), 30-90% (G3), >90% (G4), respectively, and completely. Results: In B-mode examination partial response was observed in 9/13 cases (completely, G1, G3, G4), and stable disease was demonstrated in 3/13 cases (completely, G1, G4). Complete response was found in 1/13 cases. As for backscatter coefficient, 10/13 tumors (completely, and G2, G3, and G4) were characterized by an increased mean value of 153%. Three tumors 3/13 (G1) displayed a decreased mean value of 31%. Conclusion: The variability of backscatter coefficient, could be associated with alterations in the structure of the tumor tissue during neoadjuvant chemotherapy. There were unequivocal differences between responded and non-responded patients. The backscatter coefficient analysis correlated better with the results of histopathological verification than with the B-mode RECIST criteria.

Objective: Neoadjuvant chemotherapy was initially used in locally advanced breast cancer, and currently it is recommended for patients with Stage 3 and with early-stage disease with human epidermal growth factor receptors positive or triple-negative breast cancer. Ultrasound imaging in combination with a quantitative ultrasound method is a novel diagnostic approach. Aim of study: The aim of this study was to analyze the variability of the integrated backscatter coefficient, and to evaluate their use to predict the effectiveness of treatment and compare to ultrasound examination results. Material and method: Ten patients (mean age 52.9) with 13 breast tumors (mean dimension 41 mm) were selected for neoadjuvant chemotherapy. Ultrasound was performed before the treatment and one week after each course of neoadjuvant chemotherapy. The dimensions were assessed adopting the RECIST criteria. Tissue responses were classified as pathological response into the following categories: not responded to the treatment (G1, cell reduction by ≤9%) and responded to the treatment partially: G2, G3, G4, cell reduction by 10–29% (G2), 30–90% (G3), >90% (G4), respectively, and completely. Results: In B-mode examination partial response was observed in 9/13 cases (completely, G1, G3, G4), and stable disease was demonstrated in 3/13 cases (completely, G1, G4). Complete response was found in 1/13 cases. As for backscatter coefficient, 10/13 tumors (completely, and G2, G3, and G4) were characterized by an increased mean value of 153%. Three tumors 3/13 (G1) displayed a decreased mean value of 31%. Conclusion: The variability of backscatter coefficient, could be associated with alterations in the structure of the tumor tissue during neoadjuvant chemotherapy. There were unequivocal differences between responded and non-responded patients. The backscatter coefficient analysis correlated better with the results of histopathological verification than with the B-mode RECIST criteria.

Identification of pathological complete response after neoadjuvant chemotherapy for breast cancer: comparison of greyscale ultrasound, shear wave elastography, and MRI

AIM

To assess the value of post-treatment shear-wave elastography (SWE) parameters (maximum stiffness [Emax], mean stiffness [Emean], and standard deviation [SD]) compared to greyscale ultrasonography (US) and magnetic resonance imaging (MRI) in identifying pathological complete response (pCR) to neoadjuvant chemotherapy (NACT) in breast cancer.

MATERIALS AND METHODS

In a prospective cohort study, 80 patients receiving NACT for breast cancer underwent baseline and post-treatment US, SWE, and MRI examinations. Four SWE images in two orthogonal planes were obtained. Maximum greyscale US diameter and maximum diameter of lesion enhancement on MRI were measured. Percentage reductions between baseline and post-treatment scans were calculated for MRI and greyscale US diameter, and Emean, Emax, and SD. The percentage reduction in Emean and US diameter were also analysed as a combination. Analysis was undertaken using receiver operating characteristic (ROC) curves and the chi-squared test.

RESULTS

pCR occurred in 21 of 80 (26%) women. The area under the ROC curve (AUC) for pCR of percentage reductions in Emean, Emax, SD, and greyscale US diameter were 0.89, 0.85, 0.75, and 0.86, respectively. The combination of percentage reductions in Emean and greyscale ultrasound diameter yielded an AUC of 0.92, which is similar to the AUC for MRI of 0.96 (p=0.28).

CONCLUSIONS

SWE combined with greyscale US shows promise for end-of-treatment identification of response to NACT in women with breast cancer, with accuracies similar to breast MRI. This technique could be used to inform surgical decision-making after NACT.

Multiple-point magnetic resonance acoustic radiation force imaging

PURPOSE

To implement and evaluate an efficient multiple-point MR acoustic radiation force imaging pulse sequence that can volumetrically measure tissue displacement and evaluate tissue stiffness using focused ultrasound (FUS) radiation force.

METHODS

Bipolar motion-encoding gradients were added to a gradient-recalled echo segmented EPI pulse sequence with both 2D and 3D acquisition modes. Multiple FUS-ON images (FUS power > 0 W) were interleaved with a single FUS-OFF image (FUS power = 0 W) on the TR level, enabling simultaneous measurements of volumetric tissue displacement (by complex subtraction of the FUS-OFF image from the FUS-ON images) and proton resonance frequency shift MR thermometry (from the OFF image). Efficiency improvements included partial Fourier acquisition, parallel imaging, and encoding up to 4 different displacement positions into a single image. Experiments were performed in homogenous and dual-stiffness phantoms, and in ex vivo porcine brain.

RESULTS

In phantoms, 16-point multiple-point magnetic resonance acoustic radiation force imaging maps could be acquired in 5 s to 10 s for a 2D slice, and 60 s for a 3D volume, using parallel imaging and encoding 2 displacement positions/image. In ex vivo porcine brain, 16-point multiple-point magnetic resonance acoustic radiation force imaging maps could be acquired in 20 s for a 3D volume, using partial Fourier and parallel imaging and encoding 4 displacement positions/image. In 1 experiment it was observed that tissue displacement in ex vivo brain decreased by approximately 22% following FUS ablation.

CONCLUSION

With the described efficiency improvements it is possible to acquire volumetric multiple-point magnetic resonance acoustic radiation force imaging maps, with simultaneous proton resonance frequency shift MR thermometry maps, in clinically acceptable times.

Pre-operative stromal stiffness measured by shear wave elastography is independently associated with breast cancer-specific survival

INTRODUCTION

With the increased use of neoadjuvant therapy for breast cancer, there is a need for pre-operative prediction of prognosis. We aimed to assess the prognostic value of tumour stiffness measured by ultrasound shear wave elastography (SWE).

METHODS

A consecutive cohort of patients with invasive breast cancer underwent breast ultrasound (US) including SWE. The following were recorded prospectively: US diameter, stiffness at SWE, presentation source, core biopsy grade, oestrogen receptor (ER) status and pre-operative nodal status. Breast cancer-specific survival (BCSS) was analysed with regard to US size and stiffness, tumour grade on core biopsy, ER status, presentation mode and pre-operative nodal status. Analysis used Cox proportional hazards regression.

RESULTS

Of the 520 patients, 42 breast cancer and 53 non-breast cancer deaths were recorded at mean follow-up of 5.4 years. Hazard ratios (HR) for tertiles of stiffness were 1, 4.8 and 8.1 (P = 0.0001). HR for 2 groups based on US size < or ≥ 20 mm were 1 and 5.1 (P < 0.0001). HR for each unit increase in tumour grade on core biopsy was 3.9 (P < 0.0001). The HR for ER positivity compared to ER negativity was 0.21 (P < 0.001). BCSS was also associated with presentation mode and pre-operative nodal status. In a multivariable model, stiffness, US size and ER status were independently associated with BCSS.

CONCLUSION

Multiple pre-operative factors including stromal stiffness at SWE have independent prognostic significance. A larger dataset with longer follow-up could be used in the future to construct a pre-operative prognostic model to guide treatment decisions.

Comparison of Two Different Ultrasound Devices Using Strain Elastography Technology in the Diagnosis of Breast Lesions Related to the Histologic Results

This study was conducted to provide evidence that elastograms of two different devices and different manufacturers using the same technical approach provide the same diagnoses. A total of 110 breast lesions were prospectively analysed by two experts in ultrasound, using the strain elastography function from two different manufacturers (Hitachi HI-RTE, Hitachi Medical Systems, Wiesbaden, Germany; and Siemens eSie Touch, Siemens Medical Systems, Erlangen, Germany). Results were compared with the histopathologic results. Applying the Bowker test of symmetry, no statistically significant difference between the two elastography functions of these two devices was found (p = 0.120). The Cohen's kappa of k = 0.591 showed moderate strength of agreement between the two elastograms. The two examiners yielded moderate strength of agreement analysing the elastograms (Hitachi HI-RTE, k = 0.478; Siemens eSie Touch, k = 0.441). In conclusion, evidence is provided that elastograms of the same lesion generated by two different ultrasound devices equipped with a strain elastography function do not significantly differ.

Ultrasound elastography as an imaging biomarker for detection of early tumor response to chemotherapy in a murine breast cancer model: a feasibility study

OBJECTIVE

This study investigated the feasibility of using strain elastography (SE) and real time shear wave elastography (RT-SWE) to evaluate early tumor response to cytotoxic chemotherapy in a murine xenograft breast cancer tumor model.

METHODS

MCF-7 breast cancer-bearing nude mice were treated with either cisplatin 2 mg kg^-1 plus paclitaxel 10 mg kg^-1 (treatment group) or sterile saline (control group) once daily for 5 days. The tumor elasticity was measured by SE or RT-SWE before and after therapy. Tumor cell density was assessed by hematoxylin and eosin staining, and the ratio of collagen fibers in the tumor was evaluated by Van Gieson staining. The correlation between tumor elasticity, as determined by SE and SWE, as well as the pathological tumor responses were analyzed.

RESULTS

Chemotherapy significantly attenuated tumor growth compared to the control treatment (p < 0.05). Chemotherapy also significantly increased tumor stiffness (p < 0.05) and significantly decreased (p < 0.05) tumor cell density compared with the control. Moreover, chemotherapy significantly increased the ratio of collagen fibers (p < 0.05). Tumor stiffness was positively correlated with the ratio of collagen fibers but negatively correlated with tumor cell density.

CONCLUSION

The study suggests that ultrasound elastography by SE and SWE is a feasible tool for assessing early responses of breast cancer to chemotherapy in our murine xenograft model. Advances in knowledge: This study showed that the tumor elasticity determined by ultrasound elastography could be a feasible imaging biomarker for assessing very early therapeutic responses to chemotherapy.

Shear-wave elastography in breast ultrasonography: the state of the art

Shear-wave elastography (SWE) is a recently developed ultrasound technique that can visualize and measure tissue elasticity. In breast ultrasonography, SWE has been shown to be useful for differentiating benign breast lesions from malignant breast lesions, and it has been suggested that SWE enhances the diagnostic performance of ultrasonography, potentially improving the specificity of conventional ultrasonography using the Breast Imaging Reporting and Data System criteria. More recently, not only has SWE been proven useful for the diagnosis of breast cancer, but has also been shown to provide valuable information that can be used as a preoperative predictor of the prognosis or response to chemotherapy.

Comparison of strain and shear-wave ultrasounic elastography in predicting the pathological response to neoadjuvant chemotherapy in breast cancers

OBJECTIVE

To compare the diagnostic performances of strain elastography (SE) and shear-wave elastography (SWE) for predicting response to neoadjuvant chemotherapy (NACT) in patients with breast cancer.

METHODS

This prospective study recruited 71 eligible patients from June 2014 to May 2016. All patients provided written informed consent. Tumour stiffness was assessed by the SE strain ratio (R), SWE maximum elasticity (E_max) and SWE mean elasticity (E_mean). Ultrasonic elastography (UE) assessments were performed at each NACT cycle (t1 - t6). For the purpose of predicting, the relative changes in elastographic parameters after the first and second NACT cycles were considered as the variables [Δ(t1) and Δ(t2)]. The area under the receiver operating characteristics (AUC) curve was compared.

RESULTS

ΔE_mean(t2) and R2 displayed the best diagnostic performances within their own modalities (AUC = 0.93 and 0.90 for predicting favourable response to NACT; AUC = 0.92 and 0.78 for predicting NACT resistance, respectively). There were no significant differences in AUCs for ΔE_mean(t2) and some UE parameters (P > 0.05). By contrast, ΔE_mean(t2) was significantly superior to all other SE parameters for predicting resistance (P < 0.05).

CONCLUSIONS

SE and SWE exhibited similar performances for predicting favourable NACT responses; SWE was better than SE for predicting NACT resistance.

KEY POINTS

• Elastography parameters after the second NACT cycle showed the best diagnostic performances. • SWE and SE yielded similar diagnostic performances in predicting favourable responses. • SWE performed better than SE in predicting the pathological resistance to NACT. • Discrepant results may be due to the breast thickness and lesion depth.