Characterizing forearm skeletal muscle composition and function in breast cancer-related lymphedema using B-mode ultrasonography.

[BACKGROUND] Skeletal muscle thickness, echo intensity, and quality are important morphological properties; however, little is known how these variables compare between the affected and unaffected forearms in breast cancer-related lymphedema (BCRL).

[METHODS] Using B-mode ultrasound, we recorded the raw radiofrequency data of the affected and unaffected forearms of women (n = 20) with Stage 2 BCRL, and in a control group of 20 women with no lymphedema. The data were converted into images and measurements of skin, subcutaneous fat, and muscle thickness were obtained. Within a designated region of interest, muscle echo intensity was assessed using computer graded grey scale and muscle thickness was measured using ImageJ2. Handgrip strength was measured using standard dynamometry.

[RESULTS] We found no differences in muscle thickness among affected, unaffected, and control forearms. The affected arm had significantly lower (p ≤ 0.025) muscle quality than controls but similar to values found in the unaffected arms. The affected arm had higher muscle echo intensity than the unaffected (p ≤ 0.013) and control (p ≤ 0.001) arms. Muscle echo intensity was related to subcutaneous fat thickness (r = 0.45; p ≤ 0.05) and arm circumference (r = 0.47; p = 0.04) in the affected arm in women with lymphedema.

[CONCLUSIONS] Lymphedema does not negatively affect forearm muscle thickness. The elevated levels of muscle echo intensity of the affected arm does not influence muscle quality in BCRL. The functional relevance of an elevated muscle echo intensity in the affected arm and its relationship with arm circumference and subcutaneous fat thickness needs to be further explored.