Intra- and interrater reliability and inter-method correlations of soft tissue property measurements in the pectoral region of breast cancer survivors.

INTRODUCTION

Breast cancer treatments can alter local soft-tissue structure and mechanics, contributing to upper-limb dysfunction. Ultrasound (US) and shear-wave elastography (SWE) assess tissue stiffness, while deformation-based tools (Elastimeter, MyotonPRO) provide accessible alternatives, though their reliability and agreement are unclear. This study evaluated (1) intra- and interrater reliability of US, SWE, MyotonPRO and Elastimeter for measuring tissue thickness, composition and stiffness, and (2) correlations between SWE and deformation-based tools.

METHODS

Thirty breast cancer survivors were assessed at four pectoralis major regions on affected and non-affected sides. Skin, fat and muscle thickness, muscle composition, and stiffness were measured using US and SWE (MACH 30), with additional stiffness measures from MyotonPRO and Elastimeter. Three assessors performed repeated sessions. Reliability was analysed using ICC(3,1), SEM, %SEM, and SRD. Correlations were assessed with Spearman's coefficients.

RESULTS

Muscle thickness and composition showed weak-moderate reliability (ICC 0.237-0.766). SWE stiffness also showed weak-moderate reliability (ICC -0.032-0.539) with large measurement error. Deformation-based tools showed similar reliability (ICC 0.246-0.737), with greatest variability for MyotonPRO. No significant correlations were found between SWE and deformation-based measures.

CONCLUSION

US measurements of skin and fat thickness were most reliable. Deeper-tissue assessments showed substantial variability, likely due to anatomical complexity, probe stability and device limitations. Stiffness tools were not interchangeable.