Muscle mass loss in breast cancer patients of reproductive age (≤ 45 years) undergoing neoadjuvant chemotherapy

Purpose: Loss of muscle mass is associated with negative clinical outcome in breast cancer (BC) patients. Therefore, the aim of the study is to evaluate if there is pectoralis muscle area (PMA) depletion, reflecting loss of muscle mass, in breast cancer patients of reproductive age (≤ 45 years) undergoing neoadjuvant chemotherapy (NAC) and to correlate PMA with clinical and histopathological data. Material and methods: This monocentric study, approved by our institutional review board, enrolled a total of 52 consecutive patients (mean age 37 ± 4.96 years) with histologically proven primary breast cancer between January 2019 and September 2021, treated with NAC and in whom tumor response and PMA were assessed with breast MRI. Two radiologists calculated PMA before and after NAC independently and blindly on axial 3D FLASH pre-contrast T1-weighted images. Wilcoxon-Mann-Whitney U test compared median values and percentage changes of pectoralis muscle area at the beginning and at the end of NAC (158 ± 25.5 days). Multivariate regression analysis on ΔPMA (difference between PMA pre-NAC and PMA post-NAC) was done according to clinical and histopathological data. Inter-reader and intra-reader agreement was estimated with K statistics. Results: Pre-NAC PMA mean value was larger than post-NAC PMA mean value (9.6 ± 2.6 cm2 vs. 8.7 ± 2.2 cm2, p < 0.001, delta value 1.41). According to the RECIST criteria, no significant differences between complete and partial response were found. Multivariate regression analysis did not show any significant relationships between ΔPMA and age, time between MRI examinations, estrogen and progesterone receptor status, human epidermal growth factor receptor 2 status, Ki-67 expression, lymph node involvement, RECIST criteria, histological type, and different regimes of NAC. Inter-reader (k = 0.74) and intra-reader agreement (0.67 and 0.73) in PMA assessment was good. Conclusions: PMA variation in BC young patients, directly estimated on breast MRI, could be a potential tool to monitor body composition during NAC with potential implications in improving outcome.