Shear Wave Elastography Assessment of Neoadjuvant Chemotherapy Response in Patients With Invasive Breast Cancer

The aim of this study is to investigate the role of shear wave elastography (SWE) for early assessment of response to neoadjuvant chemotherapy in patients with invasive breast cancer.

Neoadjuvant chemotherapy (NACT) is often used to treat patients with locally advanced breast cancer, large tumor but operable breast cancer, or proven lymph node metastasis. The advantage of NACT is that it can downstage tumor size and increase the rate of breast-conserving surgery as well as providing information on the drug response through assessment of the changes of tumor size . The pathological complete response has consistently been associated with good long-term outcomes, but is achieved in only 10%-20% of cases. Patients who achieve a pathological complete response have a better prognosis than those who do not . Higher rates of pathological complete response can be achieved when selecting for certain breast cancer subtypes and treatment regimens .

Breast cancer is a heterogeneous disease that can be divided into different subtypes by immunohistochemical marker expression or gene expression array data. A new surrogate intrinsic subtype was proposed at the St Gallen meeting to separate luminal A, luminal B (HER2-/HER2+), HER2-enriched, and triple-negative disease . Similarly, tumors may have different prognosis based on their molecular subtypes. The luminal A subtype has a better prognosis than the other subtypes, and the triple-negative subgroup has the worst prognosis . On the other hand, the triple-negative subtype is more sensitive to chemotherapy than luminal A and B breast cancer .

Current techniques available for monitoring response to NACT are positron emission tomography (PET) , sonography, mammography, magnetic resonance imaging (MRI) , and shear wave elastography (SWE) . Conventional sonography and mammography have poor reliability in evaluating the size of residual tumor after chemotherapy . SWE is a recently developed low-cost imaging technique for measuring tissue stiffness in a noninvasive and quantitative manner with high reproducibility . Tissue stiffness has been demonstrated to be significantly correlated with tumor growth as cancer development and progression require extensive reorganization of the extracellular matrix (ECM) . Increased deposition of collagen and other ECM molecules enhances the stiffness of tumoral stroma . Changes in tumor stiffness were significantly greater in patients who had a good response to NACT compared to those resistant to NACT. Breast cancer pre- and post-treatment stiffness obtained from SWE was significantly correlated with the presence of residual cancer . A study in showed that the SWE stiffness measured after 3 cycles of NACT and changes in stiffness from baseline were strongly associated with pCR after 6 cycles. The combination of the post-treatment SWE and grey scale ultrasound has also been shown to be promising for end-of-treatment identification of residual disease and thus response to NACT, with similar accuracies found in assessment by MRI .

Several histopathological classifications are available to categorize the tumor response to NACT. The Miller-Payne grading (MPG) and Residual Disease in Breast and Nodes (RDBN) are systems to assess the pathological response of NACT. MPG provides a five-step scale based on tumor cellularity in the excision/mastectomy specimen compared with the pretreatment core biopsy as follows: grade 1, no reduction in overall cellularity; grade 2, minor (\<30%) loss of cellularity; grade 3, estimated 30%-90% reduction in tumor cells; grade 4, \>90% loss of tumor cells; and grade 5, no invasive carcinoma (IC); ductal carcinoma in situ may be present.\[30\] RDBN uses the following formula: level 1, pathological complete response in breast and nodes, without or with carcinoma in situ, and levels 2-4, residual disease in three different amounts, calculated as 0.2 (residual breast tumor size in cm) + the index for the involved nodes (0 for no positive nodes, 1 for 1-4 nodes, 2 for 5-7 nodes, 3 for ≥8 nodes) + the Scarff-Bloom-Richardson grade (1, 2, or 3), which takes into account tumor size, lymph node stage, and histological grade to determine response.

Eligibility Criteria:
Inclusion Criteria:

* • Histologically confirmed infiltrating breast cancer

  * Stage II or stage III disease. Nodal status must be examined by ultrasound, fine needle aspiration, sentinel node biopsy, or FDG-PET scan.
  * Age ≥18
  * Eastern Cooperative Oncology Group performance status ≤1
  * Adequate bone marrow function (ANC \>1.5 x 109/l, platelets \>100 x 109/l)
  * Adequate hepatic function (ALAT, ASAT and bilirubin \<2.5 times upper limit of normal)
  * Adequate renal function (creatinine clearance \>50 ml/min)
  * LVEF ≥50% measured by echocardiography or MUGA
  * Absence of any psychological, familial, sociological, or geographical condition potentially hampering compliance with the study protocol and follow-up schedule
  * Absence of any medical condition that would place the patient at unusual risk.
  * Signed written informed consent

Exclusion Criteria:

* • previous radiation therapy or chemotherapy

  * Other malignancy except carcinoma in situ, unless the other malignancy was treated ≥5 years ago with curative intent without the use of chemotherapy or radiation therapy.
  * Current pregnancy or breastfeeding. Women of childbearing potential must use adequate contraceptive protection.
  * Evidence of distant metastases. Evaluation of the presence of distant metastases may include chest X-ray, liver ultrasound, isotope bone-scan, CT-scan of chest and abdomen and/or FDG-PET scan, according to local procedures.
  * Evidence of bilateral infiltrating breast cancer. Evaluation of the presence of bilateral infiltrating breast cancer may include mammography, breast ultrasound and/or MRI breast.
  * Concurrent anti-cancer treatment or another investigational drug.