Characterization of body composition dynamics throughout treatment in patients with early-stage breast cancer.

This study characterized computed tomography (CT)-derived body composition and tissue morphology in females with non-metastatic breast cancer (BC), both cross-sectionally (n = 56) and longitudinally (n = 38), including comparisons with healthy women and cachexia-prone females with lung cancer. Morphologic changes occurred in the absence of pronounced muscle loss resultant of lean tissue reductions masked by concurrent increases in intra-muscular adipose. Longitudinal analyses suggest divergent phenotypes: non-cachectic patients (63% of BC cohort) demonstrated compositional shifts amid stable muscle quantity, whereas cachectic patients (37%) exhibited wasting of both muscle and adipose quantities alongside remodeling of externally-deposited adipose. Independent of weight, 32 of 38 patients with BC (84%) demonstrated clinically-relevant declines in muscle quantity and/or quality. Findings highlight the discordance between weight loss and underlying tissue dynamics, suggesting that conventional cachexia definitions may under-detect clinically relevant remodeling in early-stage BC. CT-based phenotyping may therefore refine risk stratification to better inform supportive interventions across cancer populations.