Associations of surgery type, age, and body mass index with cervicothoracic muscle viscoelastic properties after neoadjuvant taxane-based chemotherapy in patients with breast cancer: An observational study

Breast cancer treatments, including surgery and chemotherapy, may affect the musculoskeletal system even before the patient has received postoperative radiotherapy. This study aimed to investigate the viscoelastic properties of the pectoralis major (PM), upper trapezius (UT), and sternocleidomastoid (SCM) muscles in patients with breast cancer treated with neoadjuvant taxane-based chemotherapy and to examine their associations with surgery type, age, and body mass index (BMI). In this observational study, viscoelastic muscle properties of the PM, UT, and SCM muscles were assessed using the MyotonPRO (Myoton Ltd.) device in 50 patients with breast cancer who received taxane-based neoadjuvant chemotherapy followed by either total mastectomy or breast-conserving surgery. Linear mixed-effects model analyses were used to evaluate differences in muscle viscoelastic properties according to side and surgery type, with adjustment for age, BMI, time since surgery, and pain scores. PM muscle tone and stiffness were significantly higher on the affected side compared to the unaffected side (P < .05); however, surgery type was not significantly associated with the viscoelastic properties of any muscle. Age was significantly associated with the viscoelastic properties of all evaluated muscles (P < .05), except for PM and UT elasticity. BMI was significantly associated only with SCM elasticity (P < .05). Surgery type was not significantly associated with the viscoelastic properties of the cervicothoracic muscles in patients with breast cancer treated with taxane-based neoadjuvant chemotherapy. These findings suggest that patient-related factors, such as age and BMI, may be associated with variations in the mechanical properties of the cervicothoracic muscles in this population.