Abstract P3-18-15: Reliability and measurement error of breast volume calculation using 3D surface imagery
Authors: Fearn Nicola Rachel , Meybodi Farid , Kilbreath Sharon , Dylke Elizabeth , Llanos Catalina , Stuart Kirsty 
Published: March 2022

Introduction Breast volume measurement is important for oncoplastic surgery planning and measuring outcomes and side effects of both surgery and radiotherapy, including breast lymphedema. However, accurate breast volume quantification is difficult due to the shape of the breast and isolation of the breast border. Numerous techniques to quantify breast volume exist, but none have been established as a gold standard outcome measure. Three-dimensional (3D) surface imagery using VECTRA-XT can measure breast volume quickly and non-invasively. However, as measurement properties associated with quantification of breast volume using VECTRA-XT have yet to be fully determined, including extent of reliability, standard error of measurement (SEM), and smallest detectable change (SDC), the aim of this study is to determine these properties.Method A reliability study using retrospective VECTRA®-XT 3D surface images taken during clinical practice was conducted. Images from 51 women (101 breasts) before or after breast conserving surgery for breast cancer were retrieved for analysis. The breast images were taken pre-operatively in 70% of cases and following wide local excision in the remaining 30% of cases. Radiotherapy had also been performed in 20% of cases. Women were excluded if they had breast implants or mastectomy, had a breast ptosis grade of 3 (nipple was below the inferior mammary fold and close or below the lowest breast contour) or if the inferior mammary fold could not be visualised from any view of the 3D image. Three assessors trained using a standardised technique to use two software analysis programs, Vectra® 3D Analysis Module (VAM) and Breast Sculptor® software, completed the measurements. One assessor completed breast volume calculations twice (intra-rater reliability) and the remaining two assessors completed calculations once (inter-rater reliability). Results Mean breast volume for the population was 493.7cc (95%CI=469.4-517.9, range=135-1161cc) when measured by VAM and 488.7cc (95%CI= 461.2-516.2, range=104-1596cc) when measured by Breast Sculptor®. The difference in breast volume assessed using paired t-test was not statistically significant (p=0.491). Measurement of breast volume using VAM had excellent intra and inter-rater reliability with a SEM of less than 5.0% for a single rater and less than 9.0% for multiple raters. In comparison, Breast Sculptor® had excellent intra-rater reliability and substantial inter-rater reliability but the SEM was 14.3% and 20.5% for intra and inter-raters respectively (Table 1). A single rater using VAM software had the lowest SDC value indicating a change in breast volume exceeding 58.6cc would be a meaningful change in breast volume beyond measurement error.

Conclusion The reliability for the assessment of breast volume using VECTRA-XT 3D surface imagery was high when a standardised approach was used. However, the SDC, i.e. the amount of change beyond error of measurement, varied depending on which program was used and whether one or more than one rater assessed the volume. A single assessor using VAM software should be considered as the ideal in. evaluation of changes in breast volume secondary to edema, as the SDC is likely too large to detect changes using the other approaches. The project was funded by a Betty Schofield and Joyce Anderson Bequest Grant.

Table 1.Reliability, standard error of measurement and smallest detectable changeICC (95% CI)Standard error of measurement (cc)Standard error of measurement %Smallest detectable change (cc)VAM Inter-rater reliability0.961 (0.943-0.973)42.78.7118.4VAM Intra-rater reliability0.990 (0.986-0.993)21.14.258.6Breast Sculptor® Inter-rater reliability0.837 (0.785-0.880)100.220.5277.7Breast Sculptor® Intra-rater reliability0.915 (0.876-0.942)74.014.3205.2

Citation Format: Nicola Rachel Fearn, Farid Meybodi, Sharon Kilbreath, Elizabeth Dylke, Catalina Llanos, Kirsty Stuart. Reliability and measurement error of breast volume calculation using 3D surface imagery [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-15.