Changes in pectoralis major stiffness and thickness following radiotherapy for breast cancer: A 12-month follow-up case series.

Radiotherapy (RT) is a common and often essential treatment for breast cancer, but has been associated with pectoralis major (PM) muscle fibrosis and atrophy. In an initial prospective evaluation, we assessed muscle stiffness and muscle thickness of the sternocostal and clavicular regions of the PM with ultrasound shear wave elastography and B-mode imaging. Changes in PM muscle stiffness and thickness following RT can be detected within the first twelve months of RT completion. These parameters may potentially be useful for screening of patients who would benefit from post-RT physical therapy. Further studies with larger sample sizes that include patients who receive nodal radiation are necessary to confirm these findings.