Changes in body composition and muscle dysfunction are common in metastatic breast cancer (MBC). Ultrasound imaging (US) offers reliable information about muscle and fat tissue architecture (thickness) and quality (echo-intensity). This study aimed to analyze the responsiveness of thickness and echo-intensity and its possible relationship with functional and patient reported-outcomes (PRO) in MBC patients after an exercise intervention. A prospective study was conducted in 2019. A 12-week exercise program was performed, including aerobic exercise and strength training. Measurements were made at baseline and after intervention. Thickness and echo-intensity were obtained from the quadriceps and biceps brachii and brachialis (BB). Mean differences were calculated using the T-Student parametric test for dependent samples of the differences in the means before and after the intervention (p = 0.05; 95% CI). Data from 13 MBC patients showed that some US muscle variables had significant differences after intervention. Best correlations were found between the quality of life questionnaire (QLQ-BR23) PRO and variables from BB muscle thickness in contraction (r = 0.61, p < 0.01), and Non-contraction (r = 0.55, p < 0.01). BB Muscle Non-contraction Thickness also explained 70% of QLQ-BR23 variance. In conclusion, muscle architecture biomarkers showed great responsiveness and are correlated with PRO after an exercise intervention in MBC patients.
