Evaluation of Virtual Touch Tissue Imaging Quantification (VTIQ – 2D-SWE) in the Assessment of BI-RADS® 3 and 4 Lesions

Elastography is a method of imaging tissue stiffness. It is based on shear wave velocity information that can be mapped to create an image of the stiffness in the region of interest.

Sonoelastography is used to differentiate benign from malignant lesions since malignant lesions alter tissue elasticity.

Adding Shear Wave elastographic features to BI-RADS® feature analysis- especially in lesions scored BI-RADS® 3 and 4a- improved specificity of breast US mass assessment without loss of sensitivity.

The BI-RADS® categories are defined by the risk for a malignant lesion varying from benign BI-RADS® 2 lesions, up to a 2% malignancy rate in BI-RADS® 3 and 2- 95% in BI-RADS® 4 (4a 2-10%; 4b 10-50%; 4c 50-95%). Based on these probabilities, biopsies are recommended for BI-RADS® 4 and 5 lesions and short-term follow-up examinations for BI-RADS® 3. Consequently, up to 2% of the in Ultrasound visible breast cancers are not directly detected as such and put into the BI-RADS® 3 category. In contrast, in the BI-RADS® 4a category more than 90% of the biopsies are unnecessary.

The main aim of the confirmatory study is to use Virtual Touch Tissue Imaging Quantification in order to reduce unnecessary benign biopsies without a reduction of the number of detected cancers.

This multi-center study is planned to involve 12 sites in 7 countries. Recruitment started at the first sites in February 2016. Recruitment takes place in the course of the patient's routine visit at a certified breast unit. All study participants will receive VTIQ in addition to standard ultrasound.

Enrollment goal is a total of 1000 cases, split into groups of a minimum of n= 300 BI-RADS® 3, n= 400 BI-RADS® 4a, n= 100 BI-RADS® 4b, n= 100 BI-RADS® 4c. All patients will be documented in a screening list. Monitoring will be performed by the Coordination Center for Clinical Trials (KKS Heidelberg). Completeness, validity and plausibility of data will be checked in time of data entry (edit-checks) and using validating programs, which will generate queries. The investigator or the designated representatives are obliged to clarify or explain the queries. If no further corrections are to be made in the database it will be closed and used for statistical analysis. All data management procedures will be carried out on validated systems and according to the current Standard Operating Procedures (SOPs) of the Institute of Medical Biometry and Informatics.

The standard BI-RADS® Ultrasound (US) category (BI-RADS® 3-4c) and VTIQ values will be correlated with the histological result. Additionally, local (BI-RADS® given at each site) and central expert BI-RADS® assessment will be compared (BI-RADS® assessment and assessment of the variables leading to the BI-RADS® value separately) to assess the inter-rater reliability. In addition, the BI-RADS® assessments will be compared with the histological results.

The variable "measurement lesion (in m/s)" is derived from three VTIQ measurements as follows:

I. For confirmatory analysis of primary objectives an algorithm was established,

using the first measurement for analysis if the value is smaller than 2.5 m/s or if the value is larger than 4.5 m/s. If the first measurement is smaller than 2.5 m/s, the lesion can be considered benign and no further diagnostics is needed. If the lesion is larger than 4.5 m/s the lesion should be considered suspicious and further diagnostics is required.
requiring two additional measurements (in total three measurements) if the first measurement is in the range of ≥ 2.5 m/s to ≤ 4.5 m/s. In this case the average of all three measurements is used for analysis.

II. For descriptive analysis other options for derivation of this variable from the three VTIQ measurements will be calculated for discussion:

First measurement only
Average of all three measurements
Median of all three measurements
Maximum of all three measurements

In conjunction with the maximum VTIQ shear wave velocity the quality display will be used to aid in the classification of lesions as malignant or benign as follows:

If the shear wave velocity ≥ the cut-off value (3.5 m/s), the lesion is considered potentially malignant, regardless of the outcome of the quality factor
If a lesion or lesion rim has a completely high quality factor (all green) and a shear wave velocity < the cut-off value (3.5 m/s), the lesion is considered benign.
If a lesion or lesion rim has mixed high and low quality factors (there are areas with low quality within the mass) and the only area of high quality (green) has a shear wave velocity < the cut-off value (3.5 m/s), then the lesion is indeterminate and malignancy cannot be excluded.