Muscle mass loss after neoadjuvant chemotherapy in breast cancer: estimation on breast magnetic resonance imaging using pectoralis muscle area

The loss of skeletal muscle mass is widely considered a predictor of poor survival and toxicity in breast cancer patients. The aim of this study is to evaluate if there is pectoralis muscle area (PMA) variation, reflecting loss of skeletal muscle mass, on consecutive MRI examinations after neoadjuvant chemotherapy. The retrospective study protocol was approved by our institutional review board. A total of n = 110 consecutive patients (mean age 56 ± 11 years) who were treated with neoadjuvant chemotherapy (NAC) for histologically proven primary breast cancer between January 2017 and January 2019 and in whom tumor response was checked with standard breast MRI were included. Two radiologists calculated the pectoralis muscle cross-sectional area before and after NAC. Time between the MRI examinations, before starting NAC and after completing NAC, was 166.8 ± 50 days. PMA calculated pre-NAC (8.14 cm2) was larger than PMA calculated post-NAC (7.03 cm2) (p